spew vs spit up

spew and spit up both are verbs.

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

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

Other hypernyms of spew include cough out, cough up, expectorate, spit out.

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