keep back vs blink

keep back is not a noun while blink is a noun.

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

As verbs, blink is a hyponym of keep back; that is, blink is a word with a more specific, narrower meaning than keep back:

keep back (noun)	blink (noun)
	a reflex that closes and opens the eyes rapidly

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