oyster

oys·ter

noun, often attributive \ˈȯis-tər\

Definition of OYSTER

1

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

2

: something that is or can be readily made to serve one's personal ends <the world was her oyster>

3

: a small mass of muscle contained in a concavity of the pelvic bone on each side of the back of a fowl

4

: an extremely taciturn person

5

: 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

cloister, hoister, roister

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.