buxomness vs roundness

buxomness and roundness both are nouns.

Word	Noun	Adjective	Verb	Adverb
buxomness	Yes	No	No	No
roundness	Yes	No	No	No

As nouns, roundness is a hypernym of buxomness; that is, roundness is a word with a broader meaning than buxomness:

buxomness: the bodily property of being attractively plump and vigorous and (of women) full-bosomed
roundness: the bodily property of being well rounded

Other hypernyms of buxomness include embonpoint, plumpness.

buxomness (noun)	roundness (noun)
the bodily property of being attractively plump and vigorous and (of women) full-bosomed	the property possessed by a line or surface that is curved and not angular
	the bodily property of being well rounded
	the quality of being round numbers
	the fullness of a tone of voice