Feather  —n. 1 one of the structures forming a bird's plumage, with a horny stem and fine strands. 2 (collect.) A plumage. B game-birds. —v. 1 cover or line with feathers. 2 turn (an oar) edgeways through the air.  feather in one's cap a personal achievement. Feather one's nest enrich oneself. In fine (or high) feather colloq. In good spirits.  feathery adj. [old english]