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.
Anything no longer in common use or practice.