dinosaur

noun

• 1a fossil reptile of the Mesozoic era, often reaching an enormous size.

The dinosaurs are placed, according to their hip structure, in two distantly related orders (see ornithischian and saurischian). Some of them may have been warm-blooded, and their closest living relatives are the birds. Dinosaurs were all extinct by the end of the Cretaceous period (65 million years ago), possibly as a result of a catastrophic asteroid impact in the Gulf of Mexico

• 2a person or thing that is outdated or has become obsolete because of failure to adapt to changing circumstances.