double back vs turn back

double back and turn back both are verbs.

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

As verbs, double back and turn back are synonyms defined as:

Other synonyms of double back include backtrack.

double back (verb)	turn back (verb)
retrace one's course	go back to a previous state
	turn inside out or upside down
	hold back, as of a danger or an enemy; check the expansion or influence of
	retrace one's course
	force to go away; used both with concrete and metaphoric meanings