fill up vs alter

fill up and alter both are verbs.

Word	Noun	Adjective	Verb	Adverb
fill up	No	No	Yes	No
alter	No	No	Yes	No

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

Other hypernyms of fill up include change, modify.

fill up (verb)	alter (verb)
make full, also in a metaphorical sense	remove the ovaries of
become full	become different in some particular way, without permanently losing one's or its former characteristics or essence
eat until one is sated	cause to change; make different; cause a transformation
fill or stop up	insert words into texts, often falsifying it thereby
	make an alteration to