Definition from Wiktionary, the free dictionary
See also Singleton
singleton (plural singletons)
- (playing cards) A playing card that is the only one of its suit in a hand, especially at bridge.
- A single object, especially one of a group.
- (computing) A class that may not be instantiated more than once, i.e. that implements the singleton design pattern.
- (mathematics) A set with exactly one element.
- A child or animal that is born singly, not as a twin or other multiple birth.
See also 
- IPA: /ˈsɪŋɡəltɔn/, /ˈsɪŋəltɔn/
- A singleton (lone playing card).
- A singleton (design pattern, class, set).