A dog from a group of small, lively breeds, originally bred for the hunting of burrowing prey such as rats, rabbits, foxes, and even otters; this original function is reflected in some of their names (e.g. rat terrier).
Someone displaying terrier-like qualities such as determined pursuit.
Borrowed from Middle French, from Old French chien terrier (“terrier dog”), from chien (“dog”) + Old French terrier (“of earth”, adjective), from Medieval Latin terrarius (“of earth”), from Latin terra (“earth”).