shoot one's mouth off vs speak

shoot one's mouth off and speak both are verbs.

Word	Noun	Adjective	Verb	Adverb
shoot one's mouth off	No	No	Yes	No
speak	No	No	Yes	No

As verbs, speak is a hypernym of shoot one's mouth off; that is, speak is a word with a broader meaning than shoot one's mouth off:

Other hypernyms of shoot one's mouth off include mouth, talk, utter, verbalise, verbalize.

shoot one's mouth off (verb)	speak (verb)
speak spontaneously and without restraint	express in speech
	exchange thoughts; talk with
	use language
	give a speech to
	make a characteristic or natural sound