shrink back vs recoil

shrink back is not a noun while recoil is a noun.

Word	Noun	Adjective	Verb	Adverb
shrink back	No	No	Yes	No
recoil	Yes	No	Yes	No

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

Other hypernyms of shrink back include cringe, flinch, funk, quail, shrink, squinch, wince.

shrink back (noun)	recoil (noun)
	a movement back from an impact
	the backward jerk of a gun when it is fired

shrink back (verb)	recoil (verb)
pull away from a source of disgust or fear	spring back, as from a forceful thrust
	draw back, as with fear or pain
	spring back; spring away from an impact
	come back to the originator of an action with an undesired effect