dinosaur

noun

di·​no·​saur ˈdī-nə-ˌsȯr 

1

: 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.

2

: any of various large extinct reptiles (such as an ichthyosaur or mosasaur) other than the true dinosaurs

3

: one that is impractically large, out-of-date, or obsolete

The factory is now a rusting dinosaur.

dinosaurian

ˌdī-nə-ˈsȯr-ē-ən 

adjective

dinosauric

ˌdī-nə-ˈsȯr-ik 

adjective

Synonyms

• relic
• has-been

Examples of dinosaur in a Sentence

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

Boston’s ballpark was already a dinosaur when the Red Sox triumphed over the visiting Milwaukee Brewers 4-3 early in the 1990 season. —Gabrielle Starr, Boston Herald, 19 July 2025

The dinosaur bone came to light in January during a drilling project to study the layers of rock underneath the site, the museum announced on July 9. —Taylor Nicioli, CNN Money, 17 July 2025

The rise of e-commerce, particularly Amazon, led to widespread belief that traditional big-box retailers would become irrelevant dinosaurs. —Robert Daugherty, Forbes.com, 16 July 2025

Previous papers that purported to describe proteins from 68-million-year-old and 80-million-year-old dinosaur fossils were met with skepticism and pushback by academics, reports Nature. —Sara Hashemi, Smithsonian Magazine, 16 July 2025

Word History

Etymology

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

Phrases Containing dinosaur

• avian dinosaur
• duckbill dinosaur
• duck-billed dinosaur
• nonavian dinosaur

Rhymes for dinosaur

• albacore
• alongshore
• antiwar
• anymore
• blastopore
• carnivore
• commodore
• evermore
• furthermore
• guarantor
• herbivore
• heretofore

Kids Definition

dinosaur

noun

di·​no·​saur ˈdī-nə-ˌsȯr 

: any of a group of extinct often very large mostly land-dwelling long-tailed reptiles of the Mesozoic era

Etymology

derived from Greek deinos "terrible" and Greek sauros "lizard"