bunk vs head for the hills

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

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

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

bunk (noun)	head for the hills (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

bunk (verb)	head for the hills (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