flex vs crawl

flex and crawl both are nouns.

Word	Noun	Adjective	Verb	Adverb
flex	Yes	No	Yes	No
crawl	Yes	No	Yes	No

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

flex (noun)	crawl (noun)
the act of flexing	a slow mode of locomotion on hands and knees or dragging the body
	a swimming stroke; arms are moved alternately overhead accompanied by a flutter kick
	a very slow movement

flex (verb)	crawl (verb)
cause (an object) to assume a crooked or angular form	move slowly; in the case of people or animals with the body near the ground
bend a joint	swim by doing the crawl
form a curve	show submission or fear
contract	be full of
exhibit the strength of	feel as if crawling with insects