Definitions for: Singleton

[n] the playing card that is the only card in a suit held in a bridge hand as initially dealt
[n] a set containing a single member
[n] a single object (as distinguished from a pair)

Webster (1913) Definition: Sin"gle*ton, n.
In certain games at cards, as whist, a single card of any
suit held at the deal by a player; as, to lead a singleton.

See Also: 1, ace, I, one, playing card, set, single, unity