spit up vs spew

spit up and spew both are verbs.

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

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

Other hyponyms of spit up include cough, ptyalise, ptyalize, spit, spue, spit out, splutter, sputter.

spit up (verb)	spew (verb)
discharge (phlegm or sputum) from the lungs and out of the mouth	eject the contents of the stomach through the mouth
give reluctantly	expel or eject (saliva or phlegm or sputum) from the mouth
	eject or send out in large quantities, also metaphorical