gibber vs verbalize

gibber is a noun but verbalize is not a noun.

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

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

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

gibber (noun)	verbalize (noun)
unintelligible talking

gibber (verb)	verbalize (verb)
speak (about unimportant matters) rapidly and incessantly	convert into a verb
chatter inarticulately; of monkeys	express in speech
	be verbose
	articulate; either verbally or with a cry, shout, or noise