redbelly vs red-bellied terrapin

redbelly and red-bellied terrapin both are nouns.

Word	Noun	Adjective	Verb	Adverb
redbelly	Yes	No	No	No
red-bellied terrapin	Yes	No	No	No

As nouns, redbelly and red-bellied terrapin are synonyms defined as:

redbelly and red-bellied terrapin: freshwater turtle of Chesapeake Bay tributaries having red markings on the lower shell

Other synonyms of redbelly include Pseudemys rubriventris, red-bellied turtle.

redbelly (noun)	red-bellied terrapin (noun)
freshwater turtle of Chesapeake Bay tributaries having red markings on the lower shell	freshwater turtle of Chesapeake Bay tributaries having red markings on the lower shell