had·ro·saur·id 
(hăd′rə-sôrĭd)
(hăd′rə-sôrĭd)n.
Any of various herbivorous ornithischian dinosaurs of the family Hadrosauridae of the Cretaceous Period, having a broad toothless beak, numerous teeth in the back of the jaw, a stiff tail, and sometimes a crest on the head. Also called duckbill, duck-billed dinosaur, hadrosaur.
[From New Latin Hadrosauridae, family name, from Hadrosaurus, type genus; see HADROSAURUS.]
had′ro·saurid adj.