Back Door Hand
A hand that plays out differently than intended. For example a player with a pair of kings at the beginning, who then receives four additional cards of a suit matching one of the kings, has "backed in" to a flush.
Another example is a player holding two suited cards trying to make a straight when the turn and the river both come up in the same suit giving the player a flush.
A third example is where there is a showdown between a player holding Ace of Spades three of Spades against a player holding a pair of Kings. The flop shows jack of spades 10 of spades, six of diamonds. The player holding the ace three suited stays hoping to make a flush. The turn comes up as a 3 of diamonds. Now the player has several other ways to win. He can win with another spade on the river, an ace on the river, or another 3. Another three comes giving the first player trips. The possibility of getting 3 and 3 on the turn and the river is only about 1.5 percent. However the player was staying hoping to make another spade by the river where the chances are close to 40 percent. The player won with back door trips.