Wordnet 3.0
NOUN (1)
1. 
 a huge quadrupedal herbivore with long neck and tail; 
 of late Jurassic in western North America; 
WordNet (r) 3.0 (2006):
diplodocus
    n 1: a huge quadrupedal herbivore with long neck and tail; of
         late Jurassic in western North America