noun. A very large herbivorous sauropod dinosaur of the genus Apatosaurus of the Jurassic Period, having a long neck and tail and a small head.

noun. A genus of dinosaurian reptiles of the family Camarasauridæ, described by Marsh from the Upper Jurassic rocks of Colorado.

noun. a genus of extinct dinosaurs comprising the brontosaurs; apatosaurs.

noun. A very large sauropod dinosaur of the genus Apatosaurus (or Brontosaurus ) of the late Jurassic Period. Apatosaurs had a long neck and tail and a relatively small head.

noun. huge quadrupedal herbivorous dinosaur common in North America in the late Jurassic

"Here over thirteen hundred footprints of the plant-eating apatosaurus a.k.a. brontosaurus and the carnivorous three-toed allosaurus, ripple marks, a few clams, a palm frond and some horsetails, fish bones, ooids have all solidified into solid rock."