The American Heritage® Dictionary of the English Language, 4th Edition
n. A very large herbivorous dinosaur of the genus Apatosaurus (formerly Brontosaurus) of the late Jurassic period, having a long neck and tail and a relatively small head.
n. A large, herbivorous, gregarious sauropod dinosaur, of the genus Apatosaurus, from Jurassic North America; it had a long neck and tail.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. huge quadrupedal herbivorous dinosaur common in North America in the late Jurassic
Word Usage
"Allosaurus bones have been found in the quarry, suggesting the apatosaur was the main meal of the top predator of the late Jurassic not long before the plant-eaters bone, and a bit of skin, were covered up by mud."