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[dahy-nuh-sawr] /ˈdaɪ nəˌsɔr/
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.
Origin of dinosaur
< New Latin Dinosaurus (1841), originally a genus name. See dino-, -saur Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for dinosaurs
Contemporary Examples
Historical Examples
  • There is a large number of dinosaurs in which this remarkable distinctive character of Birds is also found.

    Dragons of the Air H. G. Seeley
  • Some bones of dinosaurs have also been found in the Connecticut Valley.

    Geology William J. Miller
  • Not cattle, but dinosaurs, were stampeding across the city of the Ogrum.

    The Lost Warship Robert Moore Williams
  • No dinosaurs are definitely known to have crossed the line into the Cenozoic era.

    Geology William J. Miller
  • He means that I've unloaded this corral full of Texas dinosaurs on him at nineteen a throw.

    The Sheriff's Son William MacLeod Raine
British Dictionary definitions for dinosaurs


any extinct terrestrial reptile of the orders Saurischia and Ornithischia, many of which were of gigantic size and abundant in the Mesozoic era See also saurischian, ornithischian Compare pterosaur, plesiosaur
a person or thing that is considered to be out of date
Derived Forms
dinosaurian, adjective
Word Origin
C19: from New Latin dinosaurus, from Greek deinos fearful + sauros lizard
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for dinosaurs



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.

Online Etymology Dictionary, © 2010 Douglas Harper
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dinosaurs in Science
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.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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dinosaurs in Culture

dinosaurs definition

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.

Note: Some dinosaurs were very large and had small brains — factors that may in part have led to their extinction. The term is often used to refer to something or someone that is antiquated and unable to adapt to change: “The old cavalry generals couldn't adjust to the use of tanks — they became dinosaurs.”
Note: Commonly known dinosaurs include Tyrannosaurus rex, Brontosaurus, Stegosaurus, and Triceratops.
Note: Some scientists believe that modern birds are the descendants of dinosaurs.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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