retract vs shrink back

retract and shrink back both are verbs.

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

As verbs, retract and shrink back are synonyms defined as:

retract (verb)	shrink back (verb)
formally reject or disavow a formerly held belief, usually under pressure	pull away from a source of disgust or fear
pull inward or towards a center
use a surgical instrument to hold open (the edges of a wound or an organ)
pull away from a source of disgust or fear