brontosaurus n.

one of the first well-known dinosaurs, popularly noted for its great size and small brain capacity, 1879, coined by U.S. paleontologist O.C. Marsh in Modern Latin, from Greek brontē "thunder" (perhaps from PIE imitative root *bhrem- "to growl") + -saurus. The confusion with apatosaurus dates to at least 1903 and scientists still debate whether they are the same species or not.