Any of certain marine bivalve mollusks, especially those of the family Ostreidae (the true oysters), usually found adhering to rocks or other fixed objects in shallow water along the seacoasts, or in brackish water in the mouth of rivers.
User Defined Definitions
"marine mollusks having a rough irregular shell; found on the sea bed mostly in coastal waters"
"edible body of any of numerous oysters"
"a small muscle on each side of the back of a fowl"