motormouth vs verbalizer

motormouth and verbalizer both are nouns.

Word	Noun	Adjective	Verb	Adverb
motormouth	Yes	No	No	No
verbalizer	Yes	No	No	No

As nouns, verbalizer is a hypernym of motormouth; that is, verbalizer is a word with a broader meaning than motormouth:

motormouth: someone who talks incessantly
verbalizer: someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)

Other hypernyms of motormouth include speaker, talker, utterer, verbaliser.

motormouth (noun)	verbalizer (noun)
someone who talks incessantly	someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)