/ Dictionary / Index O oyster cap: Meaning and Definition of Find definitions for: oys'ter cap" Pronunciation: [key] an edible, brownish-gray to white mushroom, Pleurotus ostreatus, that grows in clusters on fallen trees and their stumps. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. oyster bed oystercatcher Related Content Daily Word Quiz: agitated Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language