whisper vs verbalize

whisper is a noun but verbalize is not a noun.

Word	Noun	Adjective	Verb	Adverb
whisper	Yes	No	Yes	No
verbalize	No	No	Yes	No

As verbs, verbalize is a hypernym of whisper; that is, verbalize is a word with a broader meaning than whisper:

Other hypernyms of whisper include mouth, speak, talk, utter, verbalise.

whisper (noun)	verbalize (noun)
speaking softly without vibration of the vocal cords
a light noise, like the noise of silk clothing or leaves blowing in the wind

whisper (verb)	verbalize (verb)
speak softly; in a low voice	convert into a verb
	express in speech
	be verbose
	articulate; either verbally or with a cry, shout, or noise