expand vs billow

expand is not a noun while billow is a noun.

Word	Noun	Adjective	Verb	Adverb
expand	No	No	Yes	No
billow	Yes	No	Yes	No

As verbs, billow is a hyponym of expand; that is, billow is a word with a more specific, narrower meaning than expand:

Other hyponyms of expand include balloon, inflate, intumesce, swell, swell up, tumefy, tumesce.

expand (noun)	billow (noun)
	a large sea wave

expand (verb)	billow (verb)
grow vigorously	become inflated
exaggerate or make bigger	rise and move, as in waves or billows
become larger in size or volume or quantity	rise up as if in waves
expand the influence of	move with great difficulty
make bigger or wider in size, volume, or quantity
add details, as to an account or idea; clarify the meaning of and discourse in a learned way, usually in writing
extend in one or more directions