heat up vs toast

heat up is not a noun while toast is a noun.

Word	Noun	Adjective	Verb	Adverb
heat up	No	No	Yes	No
toast	Yes	No	Yes	No

As verbs, toast is a hyponym of heat up; that is, toast is a word with a more specific, narrower meaning than heat up:

Other hyponyms of heat up include crisp, crispen, scald, soak, calcine, preheat, overheat, scorch, sear, bake, broil, reheat.

heat up (noun)	toast (noun)
	slices of bread that have been toasted
	a drink in honor of or to the health of a person or event
	a celebrity who receives much acclaim and attention
	a person in desperate straits; someone doomed

heat up (verb)	toast (verb)
make hot or hotter	make brown and crisp by heating
gain heat or get hot	propose a toast to
make more intense