head for the hills vs bunk

head for the hills is not a noun while bunk is a noun.

Word	Noun	Adjective	Verb	Adverb
head for the hills	No	No	Yes	No
bunk	Yes	No	Yes	No

As verbs, head for the hills and bunk are synonyms defined as:

Other synonyms of head for the hills include break away, escape, fly the coop, hightail it, lam, run, run away, scarper, scat, take to the woods, turn tail.

head for the hills (noun)	bunk (noun)
	a bed on a ship or train; usually in tiers
	a rough bed (as at a campsite)
	beds built one above the other
	a long trough for feeding cattle
	unacceptable behavior (especially ludicrously false statements)
	a message that seems to convey no meaning

head for the hills (verb)	bunk (verb)
flee; take to one's heels; cut and run	flee; take to one's heels; cut and run
	provide with a bunk
	avoid paying