sing vs babble

sing is not a noun while babble is a noun.

Word	Noun	Adjective	Verb	Adverb
sing	No	No	Yes	No
babble	Yes	No	Yes	No

As verbs, sing and babble are synonyms defined as:

sing (noun)	babble (noun)
	gibberish resembling the sounds of a baby

sing (verb)	babble (verb)
make a whining, ringing, or whistling sound	to talk foolishly
divulge confidential information or secrets	divulge confidential information or secrets
to make melodious sounds	utter meaningless sounds, like a baby, or utter in an incoherent way
produce tones with the voice	flow in an irregular current with a bubbling noise
deliver by singing