wink vs keep back

wink is a noun but keep back is not a noun.

Word	Noun	Adjective	Verb	Adverb
wink	Yes	No	Yes	No
keep back	No	No	Yes	No

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

Other hypernyms of wink include hold back, keep, restrain.

wink (noun)	keep back (noun)
a reflex that closes and opens the eyes rapidly
closing one eye quickly as a signal
a very short time (as the time it takes the eye to blink or the heart to beat)

wink (verb)	keep back (verb)
briefly shut the eyes	prevent the action or expression of
keep back by blinking	hold back; refuse to hand over or share
signal by winking	secure and keep for possible future use or application
gleam or glow intermittently