Singleton

Noun

 * 1)  A playing card that is the only one of its suit in a hand, especially at bridge.
 * 2) A single object, especially one of a group.
 * 3)  A class that may not be instantiated more than once, i.e. that implements the singleton design pattern.
 * 4)  A set with exactly one element.

Thesaurus
ace, article, best bower, bower, cards, clubs, deck, deuce, diamonds, dummy, entity, face cards, flush, full house, hand, hearts, individual, integer, item, jack, joker, king, knave, left bower, module, pack, pair, person, persona, picture cards, playing cards, point, queen, round, royal flush, rubber, ruff, single, soul, spades, straight, trey, trick, trump, unit