GIBBERING
Verb
gibbering
present participle of gibber
Adjective
gibbering (comparative more gibbering, superlative most gibbering)
Prone to meaningless vocalization, especially excited and confused utterances, like a beast or monster.
Noun
gibbering (plural gibberings)
Manic, meaningless speech; babble.
Source: Wiktionary
GIBBER
Gib"ber, n. Etym: [From Gib to balk.]
Definition: A balky horse. Youatt.
Gib"ber, v. i. [imp. & p. p. Gibbered; p. pr. & vb. n. Gibbering.]
Etym: [Akin to jabber, and gabble.]
Definition: To speak rapidly and inarticulately. Shak.
Source: Webster’s Unabridged Dictionary 1913 Edition