A dinosaur was a prehistoric animal that lived during different periods of time.
The word "dinosaur" can refer to any of those big, usually meat-eating or plant-eating animals that roamed the earth millions of years ago. If someone says they visited a museum and saw a dinosaur fossil, they're talking about an old bone or skeleton of one of these prehistoric creatures.
How common is "dinosaur"?
Word dinosaur is considered uncommon in modern English. It has a balanced usage among all categories: speech, fiction, newspapers and academic texts.
Definitions
noun
In scientific usage, any of the animals belonging to the clade Dinosauria, especially those that existed during the Triassic, Jurassic and Cretaceous periods and are now extinct.
In non-scientific usage, any non-avian dinosaur.
Any extinct reptile, not necessarily belonging to Dinosauria, that existed between about 230 million and 65 million years ago.
A person or organisation that is very old, has very old-fashioned views, or is not willing to change and adapt.