Case
This is the last card of a certain rank that is left in the deck.

For example, say you are heads up with a player and you hold AA (a pair of aces) while he holds KT (King and Ten). The flop was ATT, giving him three tens and giving you a house of aces over tens. The turn is a blank, and the river is a ten, giving him quads. This ten would be the 'case' ten - the last ten in the deck.