gibbering

from The Collaborative International Dictionary of English v.0.48

gibber \gib"ber\ (g[i^]b"b[~e]r), v. i. [imp. & p. p. {gibbered}
   (g[i^]b"b[~e]rd); p. pr. & vb. n. {gibbering}.] [Akin to
   jabber, and gabble.]
   To speak rapidly and inarticulately. --Shak.

   Syn: jabber.
        [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

24 Moby Thesaurus words for "gibbering":
      blabbering, blabbing, blathering, chattering, drone, droning,
      gabble, gabbling, gibber, jabber, jabbering, jibber, maundering,
      mouthing, mumble, mumbling, murmuring, mutter, muttering, prating,
      prattling, susurration, whisper, whispering

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