noun \ˈdī-nə-ˌsr\

: one of many reptiles that lived on Earth millions of years ago

: someone or something that is no longer useful or current : an obsolete or out-of-date person or thing

Full Definition of DINOSAUR

:  any of a group (Dinosauria) of extinct often very large chiefly terrestrial carnivorous or herbivorous reptiles of the Mesozoic era
:  any of various large extinct reptiles (as ichthyosaurs) other than the true dinosaurs
:  one that is impractically large, out-of-date, or obsolete
di·no·sau·ri·an \ˌdī-nə-ˈsr-ē-ən\ adjective
di·no·sau·ric \-ˈsr-ik\ adjective

Examples of DINOSAUR

  1. The old factory is now a rusting dinosaur.
  2. The character she plays is a dinosaur—a former beauty queen who is living in the past.

Origin of DINOSAUR

New Latin Dinosaurus, genus name, from Greek deinos terrifying + sauros lizard — more at dire
First Known Use: 1841


noun    (Concise Encyclopedia)

Skeletons of an ornithischian dinosaur (Stegosaurus) and a saurischian dinosaur …—© Merriam-Webster Inc.

Any of the extinct reptiles that were the dominant land animals during most of the Mesozoic Era (251–65 million years ago). The various species appeared at different times, and not all overlapped. The shape of the teeth reveal whether a given dinosaur was a carnivore or an herbivore. Dinosaurs are classified as either ornithischians or saurischians, based on pelvic girdle structure. Most had a long tail, which they held straight out, apparently to maintain balance. Most, if not all, were egg layers. Some were probably warm-blooded. Dinosaur fossils have been found on every continent, including Antarctica. Most types of dinosaurs flourished until late in the Cretaceous Period (65 million years ago), then disappeared within the next million years. Two theories for the cause of this mass extinction following some 140 million years of existence are that volcanism and mountain-building cycles altered the habitat and changed the climate or that one or more asteroids hit Earth, resulting in immense dust clouds that blocked sunlight for several years. Birds and crocodiles are thought to be living descendants of the dinosaurs. See also carnosaur; sauropod.


Next Word in the Dictionary: Dinosauria
Previous Word in the Dictionary: Dinornithidae
All Words Near: dinosaur

Seen & Heard

What made you want to look up dinosaur? Please tell us where you read or heard it (including the quote, if possible).