ringneck snake vs ring-necked snake

ringneck snake and ring-necked snake both are nouns.

Word	Noun	Adjective	Verb	Adverb
ringneck snake	Yes	No	No	No
ring-necked snake	Yes	No	No	No

As nouns, ringneck snake and ring-necked snake are synonyms defined as:

ringneck snake and ring-necked snake: any of numerous small nonvenomous North American snakes with a yellow or orange ring around the neck

Other synonyms of ringneck snake include ring snake.

ringneck snake (noun)	ring-necked snake (noun)
any of numerous small nonvenomous North American snakes with a yellow or orange ring around the neck	any of numerous small nonvenomous North American snakes with a yellow or orange ring around the neck