turn back vs fall back

turn back and fall back both are verbs.

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

As verbs, fall back is a hyponym of turn back; that is, fall back is a word with a more specific, narrower meaning than turn back:

Other hyponyms of turn back include lapse, recidivate, regress, relapse, retrogress, resile, go back, recover, recuperate.

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