1. A single object (as distinguished from a pair)
   "The matching glove was lost, leaving a singleton"
    
2. A set containing a single member
   "In probability theory, a singleton event has only one possible outcome"
    
3. The playing card that is the only card in a suit held in a bridge hand as initially dealt
   "Her singleton ace of spades was a valuable card"

Derived forms: singletons

Type of: 1, I, one, playing card, set, unity

Encyclopedia: Singleton, NSW