ˈplumicornOrnith. [f. L. plūma plume, feather + cornu horn.] One of the pair of horn-like or ear-like feathers on the head of several species of owl, often called horns or ears. 1884Coues Key N. Amer. Birds (ed. 2) 503 Bubo... [Generic characters]..Plumicorns highly developed.