- any chiefly terrestrial, herbivorous or carnivorous reptile of the extinct orders Saurischia and Ornithischia, from the Mesozoic Era, certain species of which are the largest known land animals.
- something that is unwieldy in size, anachronistically outmoded, or unable to adapt to change: The old steel mill was a dinosaur that cost the company millions to operate.
- any extinct terrestrial reptile of the orders Saurischia and Ornithischia, many of which were of gigantic size and abundant in the Mesozoic eraSee also saurischian, ornithischian Compare pterosaur, plesiosaur
- a person or thing that is considered to be out of date
1841, coined in Modern Latin by Sir Richard Owen, from comb. form of Greek deinos “terrible” (see dire) + sauros “lizard” (see -saurus). Figurative sense of “person or institution not adapting to change” is from 1952.
- Any of various extinct reptiles of the orders Saurischia and Ornithischia that flourished during the Mesozoic Era. Dinosaurs were carnivorous or herbivorous, dwelled mostly on land, and varied from the size of a small dog to the largest land animals that ever lived. One group of dinosaurs evolved into birds. See more at ornithischian saurischian. See Note at bird.
Reptiles, now extinct, that were the dominant life form on Earth for many millions of years. The name dinosaur comes from the Greek words for “monstrous lizard.” Dinosaurs became extinct suddenly, about sixty-five million years ago. Scientists now believe that their extinction was caused by the impact of a large asteroid on the Earth.