gator vs crocodilian

gator and crocodilian both are nouns.

Word	Noun	Adjective	Verb	Adverb
gator	Yes	No	No	No
crocodilian	Yes	No	No	No

As nouns, crocodilian is a hypernym of gator; that is, crocodilian is a word with a broader meaning than gator:

gator: either of two amphibious reptiles related to crocodiles but with shorter broader snouts
crocodilian: extant archosaurian reptile

Other hypernyms of gator include crocodilian reptile.

gator (noun)	crocodilian (noun)
either of two amphibious reptiles related to crocodiles but with shorter broader snouts	extant archosaurian reptile