Definition of plesiosaur
: any of an order or suborder (Plesiosauria) of large carnivorous marine reptiles of the Mesozoic with dorsoventrally flattened bodies and limbs modified into flippers
Origin and Etymology of plesiosaur
ultimately from Greek plēsios close (akin to Greek pelas near) + sauros lizard
First Known Use: 1839
Seen and Heard
What made you want to look up plesiosaur? Please tell us where you read or heard it (including the quote, if possible).