venter vs underbelly

venter and underbelly both are nouns.

Word	Noun	Adjective	Verb	Adverb
venter	Yes	No	No	No
underbelly	Yes	No	No	No

As nouns, underbelly is a hyponym of venter; that is, underbelly is a word with a more specific, narrower meaning than venter:

venter: the region of the body of a vertebrate between the thorax and the pelvis
underbelly: the soft belly or underside of an animal's body

Other hyponyms of venter include underbody.

venter (noun)	underbelly (noun)
the region of the body of a vertebrate between the thorax and the pelvis	the quality of being weak or unprotected
a bulging body part (as the belly of a muscle)	the soft belly or underside of an animal's body
the womb	lower side
a speaker who expresses or gives vent to a personal opinion or grievance