Definition of "singleton"

(playing cards) A playing card that is the only one of its suit in a hand, especially at bridge.  examples

(playing cards) A hand containing only one card of a certain suit.  examples

A single object, especially one of a group.  examples

(computing) A class that may not be instantiated more than once, i.e. that implements the singleton design pattern.  examples

(mathematics) A set with exactly one element.  examples

A child or animal that is born singly, not as a twin or other multiple birth.  examples

A person without a romantic partner.  examples

A person without a dissociative identity.  examples

(phonetics) A single consonant, as opposed to a geminated consonant.  examples