bull-snake vs colubrid snake

bull-snake and colubrid snake both are nouns.

Word	Noun	Adjective	Verb	Adverb
bull-snake	Yes	No	No	No
colubrid snake	Yes	No	No	No

As nouns, colubrid snake is a hypernym of bull-snake; that is, colubrid snake is a word with a broader meaning than bull-snake:

bull-snake: any of several large harmless rodent-eating North American burrowing snakes
colubrid snake: mostly harmless temperate-to-tropical terrestrial or arboreal or aquatic snakes

Other hypernyms of bull-snake include colubrid.

bull-snake (noun)	colubrid snake (noun)
any of several large harmless rodent-eating North American burrowing snakes	mostly harmless temperate-to-tropical terrestrial or arboreal or aquatic snakes