blabber vs speak

blabber is a noun but speak is not a noun.

Word	Noun	Adjective	Verb	Adverb
blabber	Yes	No	Yes	No
speak	No	No	Yes	No

As verbs, speak is a hypernym of blabber; that is, speak is a word with a broader meaning than blabber:

Other hypernyms of blabber include mouth, talk, utter, verbalise, verbalize.

blabber (noun)	speak (noun)
one who reveals confidential information to the police or other authority

blabber (verb)	speak (verb)
speak (about unimportant matters) rapidly and incessantly	express in speech
	exchange thoughts; talk with
	use language
	give a speech to
	make a characteristic or natural sound