throw back vs sky

throw back is not a noun while sky is a noun.

Word	Noun	Adjective	Verb	Adverb
throw back	No	No	Yes	No
sky	Yes	No	Yes	No

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

Other hypernyms of throw back include flip, pitch, toss.

throw back (noun)	sky (noun)
	the atmosphere and outer space as viewed from the earth

throw back (verb)	sky (verb)
throw back with a quick, light motion	throw or toss with a light motion