di·​no·​saur ˈdī-nə-ˌsȯr How to pronounce dinosaur (audio)
: any of a group (Dinosauria) of extinct, often very large, carnivorous or herbivorous archosaurian reptiles that have the hind limbs extending directly beneath the body and include chiefly terrestrial, bipedal or quadrupedal ornithischians (such as ankylosaurs and stegosaurs) and saurischians (such as sauropods and theropods) which flourished during the Mesozoic era from the late Triassic period to the end of the Cretaceous period
The dinosaurs, which once dominated the earth, disappeared very swiftly, leaving room for tiny shrewlike creatures to crawl out of shelter and start on the road to mammalian domination of the planet. D. E. Thomsen
Most scientists now concur that at least one great extraterrestrial object struck the planet around the time the dinosaurs died out. Rick Gore
also : any of a broader group that also includes all living and extinct birds
The overwhelming majority of scientists are now convinced that birds are theropod dinosaurs James O'Donoghue

Note: Dinosaurs have traditionally been considered a separate group from birds, which evolved from dinosaurs, but modern paleontologists now view birds as survivors of a theropod lineage of dinosaurs. In this classification, all dinosaurs except birds became extinct at the end of the Cretaceous period approximately 65 million years ago, with all dinosaurs that are not birds referred to as dinosaurs or non-avian dinosaurs and birds typically referred to as avian dinosaurs.

: any of various large extinct reptiles (such as an ichthyosaur or mosasaur) other than the true dinosaurs
: one that is impractically large, out-of-date, or obsolete
The factory is now a rusting dinosaur.
dinosaurian adjective
dinosauric adjective

Example Sentences

The old factory is now a rusting dinosaur. The character she plays is a dinosaur—a former beauty queen who is living in the past.
Recent Examples on the Web Beyond the dinosaurs themselves, there are dozens of video and touch screens where visitors can learn more about the various dinosaur species, their diets, habitats and unusual physical features. Pam Kragen, San Diego Union-Tribune, 21 Oct. 2022 The new paper also added measurements from the femurs of 613 living bird specimens from 112 species and 52 specimens from four non-avian theropod dinosaur species. Margaret Osborne, Smithsonian Magazine, 27 July 2022 The other day Memphis wanted to be a dinosaur and tomorrow Navy will want to be a cat. Gil Kaufman, Billboard, 21 Sep. 2022 Meghan also shared that their son Archie was a dinosaur for Halloween and that Lilibet was dressed as a skunk. Chloe Melas, CNN, 18 Nov. 2021 All that vanished with the water some 5,000 years ago, leaving behind ancient graveyards not far from huge dinosaur fossils from Africa’s much deeper past. Paul Sereno, Chicago Tribune, 18 Oct. 2022 Paleontologists have unearthed a new dinosaur species with tiny arms. Joshua Hawkins, BGR, 9 July 2022 Carcharodontosaurid refers to a group of carnivorous theropod dinosaur species. Kyla Guilfoil, ABC News, 7 July 2022 Previous research found that dinosaur species such as M. gigas and T. rex developed smaller arms as their heads became larger. Jack Guy, CNN, 7 July 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'dinosaur.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


borrowed from presumed New Latin *dinosaurus, the base of Dinosauria, former reptile taxon, from Greek deinós "inspiring dread or awe" + -o- -o- + New Latin Sauria, former reptile suborder, from Greek saúros "lizard" + New Latin -ia -ia entry 2 — more at deinonychus, -saurus

Note: The taxonomic name Dinosauria as well as the vernacular form dinosaur were both introduced by the British biologist and paleontologist Richard Owen (1804-92) in "Report on British Fossil Reptiles. Part II," Report of the Eleventh Meeting of the British Association for the Advancement of Science ("Held at Plymouth in July 1841") (London: J. Murray, 1842), p. 103: "The combination of such characters, some, as the sacral ones [i.e., the sacral vertebrae fused into a single structure], altogether peculiar among Reptiles, others borrowed, as it were, from groups now distinct from each other, and all manifested by creatures far surpassing in size the largest of existing reptiles, will, it is presumed, be deemed sufficient ground for establishing a distinct tribe or sub-order of Saurian Reptiles, for which I would propose the name of Dinosauria. [Footnote to the above] Gr. deinòs, fearfully great; saúros, a lizard." Although Owen's "Report on British Fossil Reptiles" purports to be the record of an oral presentation given at Plymouth in July, 1841, the detailed contemporary accounts of Owen's lecture do not mention dinosaur or Dinosauria, and it is now clear that he only introduced the word with the extensively revised version of the report released in April, 1842. The background to Owen's report is analyzed by Hugh S. Torrens in "Politics and Paleontology: Richard Owen and the Invention of Dinosaurs," M. K. Brett-Surman, et al., editors, The Complete Dinosaur, 2nd edition (Indiana University Press, 2012), pp. 25-43. Offprints of Owen's article have the publication date 1841, but, as Torrens demonstrates (p. 34), this was an error (perhaps deliberately uncorrected by Owen). Owen's rendering of Greek deinós (a word with a wide semantic range) as "fearfully great" is at odds with the conventional notion that dinosaur means "terrible lizard" in Greek. Although "terrible" (i.e., terrifying) is a possible translation of deinós, it does not appear to be the meaning Owen intended.

First Known Use

1842, in the meaning defined at sense 1

Time Traveler
The first known use of dinosaur was in 1842

Dictionary Entries Near dinosaur

Cite this Entry

“Dinosaur.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/dinosaur. Accessed 30 Nov. 2022.

Kids Definition



di·​no·​saur ˈdī-nə-ˌsȯr How to pronounce dinosaur (audio)
: any of a group of extinct often very large mostly land-dwelling long-tailed reptiles of the Mesozoic era

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