fat vs rotund

fat is a noun but rotund is not a noun.

Word	Noun	Adjective	Verb	Adverb
fat	Yes	Yes	Yes	No
rotund	No	Yes	No	No

fat (noun)	rotund (noun)
excess bodily weight
a kind of body tissue containing stored fat that serves as a source of energy; it also cushions and insulates vital organs
a soft greasy substance occurring in organic tissue and consisting of a mixture of lipids (mostly triglycerides)

fat (adjective)	rotund (adjective)
having an (over)abundance of flesh	excessively fat
containing or composed of fat	(of sounds) full and rich
marked by great fruitfulness	spherical in shape
lucrative
having a relatively large diameter

fat (verb)	rotund (verb)
make fat or plump