exhaust vs spit up

exhaust is a noun but spit up is not a noun.

Word	Noun	Adjective	Verb	Adverb
exhaust	Yes	No	Yes	No
spit up	No	No	Yes	No

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

exhaust (noun)	spit up (noun)
system consisting of the parts of an engine through which burned gases or steam are discharged
gases ejected from an engine as waste products

exhaust (verb)	spit up (verb)
wear out completely	discharge (phlegm or sputum) from the lungs and out of the mouth
eliminate (a substance)	give reluctantly
use up the whole supply of
use up (resources or materials)
deplete