fall back vs turn back

fall back and turn back both are verbs.

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

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

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

fall back (verb)	turn back (verb)
go back to bad behavior	go back to a previous state
retreat	turn inside out or upside down
hang (back) or fall (behind) in movement, progress, development, etc.	hold back, as of a danger or an enemy; check the expansion or influence of
fall backwards and down	retrace one's course
move back and away from	force to go away; used both with concrete and metaphoric meanings
have recourse to