Any marine bivalve mollusk of the genus Ostrea. They are usually found adhering to rocks or other fixed objects in shallow water along the seacoasts, or in brackish water in the mouth of rivers. The common European oyster (Ostrea edulis), and the American oyster (Ostrea Virginiana), are the most important species.
- Any of several edible bivalve mollusks of the family Ostreidae, especially of the genera Crassostrea and Ostrea, that live chiefly in shallow marine waters and have a rough, irregularly shaped shell.
- Any of various similar or related bivalve mollusks, such as the pearl oyster.
- An edible bit of muscle found in the hollow of the pelvic bone of a fowl.
- A special delicacy.
- Something from which benefits may be extracted.
- Slang A close-mouthed person.
- To gather, dredge for, or raise oysters.