Definitions

1. noun

An extinct marine reptile of the order Sauropterygia, characterized by a long neck and tail, and a pair of flippers.

“The discovery of the plesiosaur’s skeleton revealed an entirely new species of marine reptile.”

2. noun

A type of fictional sea monster, often depicted as a large reptile or aquatic creature.

“In the movie, the plesiosaur was a terrifying sea creature that attacked the ship.”