Singleton

In poker, a singleton is a card whose rank does not match that of any other in a hand.

For example, if a player has 5 and K♢ as his hole cards and 5, 7, 5♢, 7♢, and 2 come up during the flop, fourth street, and river, then the king and the 2 are singletons.

Singleton:

•  a card whose rank does not match that of any other in a hand.