any of an extinct group (order Sauropterygia) of large water reptiles of the Mesozoic Era, characterized by a small head, long neck, short tail, and four paddlelike limbs
Webster’s New World College Dictionary, Fourth Edition, compiled by the
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Word origin of 'plesiosaur'
< ModL Plesiosaurus
< Gr plēsios
, close, near, akin to pelos
, near (prob. < IE base *pel-
, to push > felt1
, L pellere
, to drive) + -saur