1.NounThose animals of the clade Dinosauria that existed during the Triassic, Jurassic and Cretaceous periods and are now extinct. .mw-parser-output .defdate{font-size:smaller}
"Despite what some cartoons portray, no humans were around when dinosaurs roamed the Earth."
2.NounAny of the animals belonging to the clade Dinosauria, including its sole surviving lineage: Neornithes.
"Many people love their backyard birds, but some of us may not realize that those feathery friends are also literally dinosaurs, in a biologically accurate sense of that word."
3.NounAny extinct reptile, not necessarily belonging to Dinosauria, that existed between about 230 million and 65 million years ago, as well as the stem-mammal Dimetrodon.
"Pterosaurs, plesiosaurs, icthyosaurs — I don't know, they're all dinosaurs to me!"
4.NounSomeone or something that is very old or old-fashioned, especially someone who is not willing to change and adapt.
"She may be a tough old bird, but it's a mistake to write her off as a dinosaur; you do so at your own risk."
5.NounAnything no longer in common use or practice.
"I couldn't believe it when I saw the equipment that they were still using. Those machines were all dinosaurs, but they were busily cranking out production."