built in bed vs bunk

built in bed and bunk both are nouns.

Word	Noun	Adjective	Verb	Adverb
built in bed	Yes	No	No	No
bunk	Yes	No	Yes	No

As nouns, built in bed and bunk are synonyms defined as:

Other synonyms of built in bed include berth.

built in bed (noun)	bunk (noun)
a bed on a ship or train; usually in tiers	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

built in bed (verb)	bunk (verb)
	flee; take to one's heels; cut and run
	provide with a bunk
	avoid paying