noun, often attributive \ˈis-tər\

: a type of shellfish that has a rough shell with two parts and that is eaten both cooked and raw

Full Definition of OYSTER

a :  any of various marine bivalve mollusks (family Ostreidae) that have a rough irregular shell closed by a single adductor muscle and include commercially important shellfish
b :  any of various mollusks resembling or related to the oysters
:  something that is or can be readily made to serve one's personal ends <the world was her oyster>
:  a small mass of muscle contained in a concavity of the pelvic bone on each side of the back of a fowl
:  an extremely taciturn person
:  a grayish-white color

Origin of OYSTER

Middle English oistre, from Anglo-French, from Latin ostrea, from Greek ostreon; akin to Greek ostrakon shell, osteon bone — more at osseous
First Known Use: 13th century

Rhymes with OYSTER


noun    (Concise Encyclopedia)

European flat oyster (Ostrea edulis)—G. Tomsich/Photo Researchers

Any bivalve of two families, Ostreidae (true oysters) or Aviculidae (pearl oysters), found in temperate and warm coastal waters worldwide. Both valves (halves) have a rough, often dirty-gray outer surface and a smooth white inner lining (nacre). The lower valve, which affixes to a surface, is nearly flat. The smaller upper valve is convex and has rougher edges. The oyster filters its food, minute organic particles, from the water. Cultivated as food, oysters are regarded as a delicacy. Pearls are the accumulation of nacre around a piece of foreign matter.


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