An uncommon thing

WordNet Word definitions in WordNet
n. a rare or unique person [syn: rare bird ]

Wiktionary Word definitions in Wiktionary
n. A rare or unique person or thing.

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
c.1600, "peculiar person," from Latin rara avis , literally "strange bird," from rara , fem. of rarus "rare" (see rare (adj.1)) + avis "bird" (see aviary ). Latin plural is raræ aves . Horace's peacock (a Roman delicacy), Juvenal's black swan ( "Rara avis ...

Wikipedia Word definitions in Wikipedia