Table talk (cards)
In certain card games, table talk is communication by a player with another player about the cards in their hand, usually contrary to the rules of the game. Such communication may be through explicitly naming cards, but it is far more common to try to give hints which the opposing players will think innocent, but which will be understood by the player's partner.
Two Player Table Talk
Table talk is when a player conveys how their partner should play their next hand either by directly saying or by making hints as to the best card to play, in order to gain an advantage over the other team. In some games a player may modify the way they play in order to convey information about their hand to their partner. This is considered acceptable and is not termed table talk, even though the distinguishing line may be very fine. For instance, a 500 player might place a bid of six no trumps to indicate that he holds the joker; this would be acceptable. However, he might modify the tone of voice when making a bid to indicate to his partner that something about the bid is significant (the suit, or perhaps that he does not wish to win it).
Hearts
In the game of Hearts, it is generally unacceptable to talk about the location of the queen of spades or notifying other players of someone threatening to "shoot the moon". Whether this type of table talk is acceptable will depend on the game, the players and the stakes. It is likely to be at least considered unsporting in any but the most light-hearted, social or drunken games.
Pinochle
Pinochle is a card game with pre-play meld bidding. Pre-arranged fake meld bids are a kind of sneaky table talk and considered definitely cheating.