A calque, equivalent to black + swan. Roman satirist Juvenal wrote in AD 82 of rara avis in terris nigroque simillima cygno ("a rare bird in the lands, and very like a black swan"), creating a durable metaphor and expression.
- Cygnus atratus, an Australian swan whose feathers are black. [c. 1700]
- Something believed impossible or not to exist, of which an example is subsequently found.
- For usage examples of this term, see Citations:black swan.
- (Cygnus atratus): Chenopis atratus
something believed non-existent