oys·ter / ˈoistər/ • n. 1. any of a number of bivalve mollusks with rough irregular shells. Several kinds are eaten (esp. raw) as a delicacy and may be farmed for food or pearls, in particular: ∎  a true oyster (family Ostreidae), including the edible American oyster (Crassostrea virginica). ∎  a similar bivalve of another family, esp. the thorny oysters (Spondylidae), wing oysters (Pteriidae), and saddle oysters (Anomiidae). 2. an oyster-shaped morsel of meat on each side of the backbone in poultry.3. (also oyster white) a shade of grayish white.• v. [intr.] raise, dredge, or gather oysters.• adj. of the color oyster white.PHRASES: the world is your oyster you are in a position to take the opportunities that life has to offer.ORIGIN: Middle English: from Old French oistre, via Latin from Greek ostreon; related to osteon ‘bone’ and ostrakon ‘shell or tile.’

oyster Marine bivalve mollusc, Ostreidae and Crassostrea spp. One dozen oysters (120 g of the edible portion) are an exceptionally rich source of vitamin B₁₂; a rich source of iron, iodine, selenium, and vitamin D; a good source of protein and niacin; a source of vitamins A, B₁, and B₂, and supply 85 kcal (360 kJ).

oyster taken proverbially as the type of someone who is reserved and uncommunicative.
don't eat oysters unless there is an R in the month from the tradition that oysters were likely to be unsafe to eat in the warmer months between May and August.

See also the world is one's oyster.

oyster Edible bivalve mollusc found worldwide in temperate and warm seas. The European flat, or edible, oyster Ostrea edulis occurs throughout coastal waters. The pearl oyster (Pinctada fucats) produces cultured pearls.

oyster XIV. ME. oistre — OF. oistre, uistre (mod. huitre) — L. ostrea (whence also OE. ostre), also ostreum — Gr. óstreon, rel. to ostéon bone.