any of several edible, marine, bivalve mollusks of the family Ostreidae, having an irregularly shaped shell, occurring on the bottom or adhering to rocks or other objects in shallow water.

the oyster-shaped bit of dark meat in the front hollow of the side bone of a fowl.

Slang . a closemouthed or uncommunicative person, esp. one who keeps secrets well.

something from which a person may extract or derive advantage

The world is my oyster.

oyster white.

to dredge for or otherwise take oysters.

noun

bivalve , mollusk , shellfish