straighten out vs comb

straighten out is not a noun while comb is a noun.

Word	Noun	Adjective	Verb	Adverb
straighten out	No	No	Yes	No
comb	Yes	No	Yes	No

As verbs, comb is a hyponym of straighten out; that is, comb is a word with a more specific, narrower meaning than straighten out:

Other hyponyms of straighten out include untwist, unbend, extend, channelise, channelize, untwine, unweave.

straighten out (noun)	comb (noun)
	the act of drawing a comb through hair
	ciliated comb-like swimming plate of a ctenophore
	the fleshy red crest on the head of the domestic fowl and other gallinaceous birds
	a flat device with narrow pointed teeth on one edge; disentangles or arranges hair
	any of several tools for straightening fibers

straighten out (verb)	comb (verb)
put (things or places) in order	smoothen and neaten with or as with a comb
settle or put right	search thoroughly
change for the better	straighten with a comb
make free from confusion or ambiguity; make clear
make straight
extricate from entanglement