ward off vs forestall

ward off and forestall both are verbs.

Word	Noun	Adjective	Verb	Adverb
ward off	No	No	Yes	No
forestall	No	No	Yes	No

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

ward off: 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 ward off include forbid, foreclose, preclude, prevent.

ward off (verb)	forestall (verb)
avert, turn away, or repel	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