oys·ter 
(oistər)
(oistər)n.
1.
a. Any of several edible bivalve mollusks of the family Ostreidae, having a rough, irregularly shaped shell attached to the substrate in shallow marine waters. Oysters are widely cultivated for food.
b. Any of various similar or related bivalve mollusks, such as the pearl oyster.
2. An edible bit of muscle found in the hollow of the pelvic bone of a fowl.
3.
a. A special delicacy.
b. Something from which benefits may be extracted.
4. Slang A close-mouthed person.
intr.v. oys·tered, oys·ter·ing, oys·ters
To gather, dredge for, or raise oysters.
[Middle English oistre, from Old French, from Latin ostreum, ostrea, from Greek ostreon; see ost- in the Appendix of Indo-European roots.]