What bridge players say and what they mean by it:

ACBL American Contract Bridge League.  The overlords of bridge in the US.  Their website has many useful resources.
Advancer Overcaller's partner.
Alert An announcement that a bid has an unusual or unexpected meaning.  When not using screens, alerts are made by the bidder's partner. Essentially this says "warning, that bid might not mean what you think it means."
Announced A requirement that something be said when a bid is made.  For example, when player opens 1NT, partner should announce the point range.  Announced bids are shown in blue on the standard ACBL Convention Card.
Authorized Information (AI) Information about the hand that one gains by legal bids and plays made by partner or by (almost) any action taken by the opponents.
Artificial A bid that has a special meaning that is unrelated to the bid's strain.
Balanced A hand with about the same number of cards in each suit.  Often summarized as "no singletons or voids and at most one doubleton."  Shapes included in this category are 4333, 4432, and 5332.  Altogether, balanced hands make up 47.6% of all hands. Some players and systems group 22(54) hands (5/4 in the minors, 2 in each major) in here as well.
BAM Board-A-Match.  A form of bridge scoring similar to matchpoints except each board is played only twice.  Thus, each pair has only three possible results: win, lose, or tie.  It is thought to be the hardest type of scoring.
Beer Card The 7.  There are different versions of how the beer card works, but the basic idea is this:  If declarer makes his contract and wins the last trick with the 7, his partner owes him a beer.  If the defense sets the contract and one defender wins the last trick with the 7, his partner owes him a beer.  These rules do not apply if are trump unless the contract is a slam.
Bid A call that mentions a strain and level.  That is, 1, 7NT, and all those other guys in between.  Note that Pass, Double, and Redouble are not technically bids (see "call"), but this distinction is not important in most cases.
BIT Break In Tempo.  A hesitation prior to making a call.  The inference that this player was considering other options may not be used by his partner to determine the next course of action.
Blitz To win all of the victory points in a Swiss Teams match.
Blocked A situation in which a suit cannot be played for as many tricks as there are winners due to a lack of communication between the hands.  For example, holding QJ1098 opposite AK.  Without another way to get back to the first hand, only 2 tricks can be taken in this suit despite the first hand holding 5 winners.
Break A description of how the outstanding cards in a suit are split between the opponents. For example, holding 8 cards in a suit, a 4-1 break indicates that one opponent held 4 of the 5 outstanding cards, the other defender only 1.
Call Either a bid, double, redouble, or pass.  Note that "bid" is often used when the technically correct term is "call," but no one really cares about this distinction except directors, and then only when the rules apply differently.
CHO The Center Hand Opponent, that is to say, partner.
Communication The ability to move between the two hands of a partnership, particularly so as to score all of the available tricks.
Competitive Auction An auction where both partnerships are bidding.
Constructive Auction An auction where the opponents keep their mouths shut and use the green cards a lot.
Contract Declarer's goal.  The contract is specified by a level (1-7) and a strain (a suit or no trump).  To make the contract, declarer must take a number of tricks equal to the level plus 6.
Convention A bid with a special meaning that is unrelated to its strain or level. 
Convention Card A form that summarizes the conventions used by a partnership.  Most ACBL tournaments require each pair to have one filled out.
Convention Disruption (CD) What happens when the bidding partners disagree about the conventional (or not) meaning of their bid(s). This usually leads to bad results, director calls, or both. Try to avoid these!
Coup Any one of a set of advanced, technical plays.
Cue Bid 1. Bidding a suit known to be held by the opponents.
2. A bid that suggests control of, rather than length in, the suit named.
Dealer The first player to act in the bidding.  Not really related to who actually passed out the cards.
Declarer The player who plays cards for the offense (himself and dummy).  The first player on the offensive side who bids the strain that eventually becomes trump.
Defender Either of the players trying to prevent declarer from making the contract.
Director The one running the game.  They're there to help you, be nice to them (at least until they rule incorrectly against you... even then be nice to their face).
Director Call To call the director over to your table for help after an irregularity.
Discard To play a card that is not trumps or the suit led or the card so played.
Distribution Usually refers to hand-pattern, the number of cards held in each suit.  It can also refer to the distribution of a single suit amongst the four hands.
Double Literally, this bid increases the reward for making a contract and the penalty for being set.  It is often used as a conventional call to spur partner to some kind of action.
Double-Dummy Having all cards exposed.  The term originates since with one's own hand and two dummy hands, all remaining cards must be in the 4th hand so the positions of all cards are known.
Doubleton A suit holding of exactly 2 cards.
Down A contract that did not make.  To "go down" is to not make.
Duck To play low to a trick, or to deliberately give up a trick that could have been won.
Dummy Declarer's partner.  Gets to turn cards and not much else.
Endplay A play in which a specific opponent is forced to be on lead at a time when any lead by him will give up a trick.  Also, the act of so putting an opponent on lead.
Entry A card in one of a partnership's hands that allows the lead to be transferred to that hand.  Manage these carefully!
Finesse The simplest nontrivial play. A simple example is holding 32 opposite AQ.  A small card is led toward the AQ and the Q is played unless the K shows up first.  If the left hand opponent has the K, the Q will score.
Fixed Getting a bad result despite having done everything right on a board.  Often by virtue of the opponents making an excellent play that no one else finds or by having the opponents make a poor play that happens to work (the latter is particularly annoying).
Forcing A bid that, by logic or by agreement, may not be passed by partner.  Passing forcing bids is a good way to make partner mad.
Game 3NT and contracts of 4 and above.  Game applies when the tricks bid are worth at least 100 points.  Bidding and making game nets a 300 point bonus when not vulnerable and a 500 point bonus vulnerable.
Green Card The Pass card.  If you've seen a bidding box, you understand.
HCP High Card Points - A method of hand evaluation in which aces are worth 4 points each, kings 3 each, queens 2 each, and jacks 1 each.  It's imperfect, but pretty good.
Hook Finesse
IMP International Match Point - a method of scoring mostly used in team games in which the score difference on a given hand is converted to a smaller scale.  The scaling prevents one or two big hands from determining an entire match.  (This can still happen in short matches though)
Interfere That annoying thing the opponents do by bidding in your auction, thereby disrupting your methods.
Irregularity Something happening outside the rules of bridge.  Leads out of turn, revokes, and other weirdnesses fall into this category.
Knockout A type of tournament in which teams play head-to-head matches with the loser being eliminated.
Lead The first card of a trick.  The "opening lead" is the lead to the first trick and is made without the benefit of seeing dummy.
Level The number part of a bid, one through seven.
LHO Left Hand Opponent
Limiting Bid A bid that reduces the possible values of a hand to a narrow range.  This is usually a very good thing.
Loser A card that will potentially lose the trick on which it is played, without regard to potential ruffs.
Losing Trick Count A way to evaluate hands.  In each suit only the top three cards are considered, and one loser is counted for each missing top honor.  For more precision, half-losers can be counted based on where the missing honors might be.
Major Suit Hearts or Spades.  Each trick in these suits is worth 30 points.
Make To win enough tricks to satisfy the contract and score the points.
Matchpoints A common method of scoring in pair games.  A pair scores 1 point on the board for each other pair holding the same cards that they beat and half a point for each such pair they tie.
Minor Suit Clubs and Diamonds.  Each trick in these suits is worth 20 points.
Misinformation (MI) A misexplanation of a partnership's agreements to their opponents.
Moysian (Fit) A 4-3 trump fit.  Named for Sonny Moyse who liked them.
No Trump The highest strain.  The first trick in a no trump contract is worth 40 points, and subsequent ones are 30.
Off the Rails Used to describe an auction in which one or both members of the bidding partnership have no idea what the other's bids mean.  Usually leads to very bad results.
Opener The first person to make a bid (not pass, pass is not a bid... see "call").
Overcall To make a bid after one or both opponents have bid first.  Overcaller is the first player to do this.
Overruff To ruff with a higher trump after another player has already ruffed on a trick.
Overtricks Tricks made in excess of the minimum needed to make the contract.
Partner The player across from you.  He or she is on your side, even though it may not always seem so.
Part Score (Partial) A contract below game.  In duplicate, making a part score nets a 50 point bonus.
Pointy Suits Spades and Diamonds, so called because they have pointy tops.
Preempt To take up a lot of bidding room quickly so as to make it difficult for the opponents to find their best contract.
Psych To intentionally make a bid that is a complete and total lie, or the actual bid so made.  Used to try and throw the opponents off track.  Use sparingly.
Responder Opener's partner.
Reverse Rebidding a higher ranked suit at a higher level then the previous bid, forcing partner to go to a higher level to take a preference to the first suit.  Used to show extra values.
For a rule of thumb: if you bypass a legal bid bid of your first suit to bid a higher-ranking 2nd suit, then it is a reverse.
Revoke A failure to follow suit when able to do so.  Don't do this, it's bad.
RHO Right Hand Opponent
Round Suits Hearts and Clubs, so called because they have round tops.
Ruff To play a trump on a trick.
Sacrifice (sac) To bid over the opponents' contract knowing you will go down in the hope that the penalty for doing so is less than the bonus the opponents would have gotten for their contract.
Set To defeat the contract.
Shape Distribution
Signal A meaning conveyed from one defender to his partner by a choice of card played.
Singleton A suit holding of but a single card.
Slam A contract at the 6 level or higher.  The 6-level contracts are small slams and get bonuses of 500 non-vulnerable and 750 vulnerable.  7-level contracts are grand slams and get bonuses of 1000 non-vulnerable and 1500 vulnerable.
Sluff Discard.
Squeeze A technical play in which a defender is forced to make a discard that gives up a trick.
Stiff A singleton
Straight-Ahead Opponent Partner
Strain A suit or no trump.
Striped-Tail Ape Double To double the opponents in game in the hopes that they won't bid their making slam (which is worth more).  The doubler plans to run (like a striped-tailed ape) if the opponents redouble.
Suit One of Clubs , Diamonds, , Hearts , or Spades
Swiss Teams A team event consisting of several rounds of head-to-head play.  The matchups are determined by how well each team is doing, with teams pitted against others with similar scores.
System An assignment of meanings, both natural and conventional, to sequences of bids that allows a partnership to communicate information about their hands.
Tap the Table Pass
Tight "Only" used when describing a suit holding.  "Ace-king tight" means holding only the ace and king and no other cards in that suit.
Treatment A natural bid that means essentially what it sounds like, but can have extra meaning, for example "forcing."
Trick Each player contributing one card.
Unauthorized Information (UI) Information obtained through means other than the actions of the opponents or the bids and plays made by partner.
Underruff To ruff with a lower trump when another player has already ruffed. This is usually a fairly pointless thing to do.
Undertricks Number of tricks made less than the number required to make the contract.
Victory Points A scoring system used in team events in which the difference in IMPs at the end of a match determines how the two teams split the available points.
Void A suit holding with no cards.
Winner A card that will win its trick (if not ruffed).  A card held in a suit in which the opponents have no higher cards.