mouth off vs rave

mouth off is not a noun while rave is a noun.

Word	Noun	Adjective	Verb	Adverb
mouth off	No	No	Yes	No
rave	Yes	No	Yes	No

As verbs, mouth off and rave are synonyms defined as:

Other synonyms of mouth off include jabber, rabbit on, rant, spout.

mouth off (noun)	rave (noun)
	an extravagantly enthusiastic review
	a dance party that lasts all night and electronically synthesized music is played

mouth off (verb)	rave (verb)
talk in a noisy, excited, or declamatory manner	praise enthusiastically
	talk in a noisy, excited, or declamatory manner
	participate in an all-night techno dance party