fall back vs revert

fall back and revert both are verbs.

Word	Noun	Adjective	Verb	Adverb
fall back	No	No	Yes	No
revert	No	No	Yes	No

As verbs, revert is a hypernym of fall back; that is, revert is a word with a broader meaning than fall back:

Other hypernyms of fall back include regress, retrovert, return, turn back.

fall back (verb)	revert (verb)
go back to bad behavior	go back to a previous state
retreat	undergo reversion, as in a mutation
hang (back) or fall (behind) in movement, progress, development, etc.
fall backwards and down
move back and away from
have recourse to