drop off vs fall back

drop off and fall back both are verbs.

Word	Noun	Adjective	Verb	Adverb
drop off	No	No	Yes	No
fall back	No	No	Yes	No

As verbs, drop off and fall back are synonyms defined as:

Other synonyms of drop off include fall behind, recede.

drop off (verb)	fall back (verb)
change from a waking to a sleeping state	go back to bad behavior
fall to a lower standard	retreat
fall or diminish	hang (back) or fall (behind) in movement, progress, development, etc.
retreat	fall backwards and down
remove (cargo, people, etc.) from and leave	move back and away from
	have recourse to