avert vs forestall

avert and forestall both are verbs.

Word	Noun	Adjective	Verb	Adverb
avert	No	No	Yes	No
forestall	No	No	Yes	No

As verbs, forestall is a hypernym of avert; that is, forestall is a word with a broader meaning than avert:

avert: prevent the occurrence of; prevent from happening; to protect from or to keep away anything undesirable; to ward off
forestall: keep from happening or arising; make impossible

Other hypernyms of avert include forbid, foreclose, preclude, prevent.

avert (verb)	forestall (verb)
turn away or aside	act in advance of; deal with ahead of time
prevent the occurrence of; prevent from happening; to protect from or to keep away anything undesirable; to ward off	keep from happening or arising; make impossible