motormouth vs verbaliser

motormouth and verbaliser both are nouns.

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

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

motormouth: someone who talks incessantly
verbaliser: 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, verbalizer.

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