toast vs heat up

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

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

As verbs, heat up is a hypernym of toast; that is, heat up is a word with a broader meaning than toast:

Other hypernyms of toast include heat.

toast (noun)	heat up (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

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