I
Inside Straight Four cards which require another between the top and the bottom card to complete a straight. Players who catch this card make an Inside Straight.

J
Jackpot Poker A form of poker in which the cardroom or casino offers a jackpot to a player who has lost with a really big hand (usually Aces full or better).
Jacks-or- Better A form of poker in which a player needs to have at least a pair of jacks to open the betting.

K
Kansas City Lowball Form of lowball poker in which the worst poker hand (2, 3, 4, 5, 7 of different suits)
is the best hand. It's also known as Deuce to Seven.
Keep Them Honest To call at the end of a hand to prevent someone from bluffing.
Key Card A card that gives you a big draw or makes your hand.
Key Hand In a session or tournament, the one hand that ends up being a turning point for the player, either for better or worse.
Kicker The highest unpaired side card in a players' hand. Kick It Raise.
Kill Pot A method to stimulate action. It is a forced bet by someone who has just won a pot(s).
Knock Check.
Kojak A hand that contains a K-J.

L
Ladies Two Queens.
Late Position Position on a round of betting where the player must act after most of the other players have acted (usually considered to be the two positions next to the button).
Lay Down Your Hand When a player folds.
Lead The first player to bet into a pot.
Limit Poker A game that has fixed minimum and maximum betting intervals along with a prescribed number of raises.
Limper The first player who calls a bet.
Limp In To enter the pot by calling rather than raising. (The usual concept of "Limp In" is when the first person to speak just calls the Big Blind.)
Live Blind An instance where the player puts in a dark bet and is allowed to raise, even if no other player raises. It's also known as an "option".
Live Card(s) In Stud Games, cards that have not yet been seen and are presumed to still be in play.
Live Hand A hand that could still win the pot.
Live One A not so knowledgeable player who plays a lot of hands.
Look When a player calls the final bet before the showdown.
Loose Is a player who plays a lot hands.
Lowball Is a form of draw poker in which the lowest hand wins the pot.