fill out vs alter

fill out and alter both are verbs.

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

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

Other hypernyms of fill out include change, modify.

fill out (verb)	alter (verb)
become round, plump, or shapely	remove the ovaries of
make bigger or better or more complete	become different in some particular way, without permanently losing one's or its former characteristics or essence
write all the required information onto a form	cause to change; make different; cause a transformation
make fat or plump	insert words into texts, often falsifying it thereby
line or stuff with soft material	make an alteration to
supplement what is thought to be deficient