black swan

noun

1. an Australian swan, Cygnus atratus, having mostly black plumage and a red bill.

2. an occurrence or phenomenon that comes as a surprise because it was not predicted or was hard to predict (often used attributively).

   a disastrous black-swan event that only appeared obvious in hindsight.

black swan

noun

1. a large Australian swan, Cygnus atratus , that has a black plumage and red bill

2. a phenomenon that occurs even though it had been thought to be impossible

Word History and Origins

Origin of black swan¹

black swan ( def. 2 ) from the belief that all swans were white, before the first sighting of Australian black swans

Word History and Origins

Origin of black swan¹

sense 2 from the fact all swans were thought to be white until black swans were discovered in Australia