The Collaborative International Dictionary of English v.0.48:

Gabble \Gab"ble\, v. i. [imp. & p. p. Gabbled; p. pr. & vb. n.
   Gabbling.] [Freq. of gab. See Gab, v. i.]
   1. To talk fast, or to talk without meaning; to prate; to
      jabber. --Shak.
      [1913 Webster]

   2. To utter inarticulate sounds with rapidity; -- used of
      fowls as well as people; as, gabbling geese.
      [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Gabble \Gab"ble\, n.
   1. Loud or rapid talk without meaning.
      [1913 Webster]

            Forthwith a hideous gabble rises loud
            Among the builders.                   --Milton.
      [1913 Webster]

   2. Inarticulate sounds rapidly uttered; as of fowls.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gabble
    n 1: rapid and indistinct speech [syn: jabber, jabbering,
         gabble]
    v 1: speak (about unimportant matters) rapidly and incessantly
         [syn: chatter, piffle, palaver, prate, tittle-
         tattle, twaddle, clack, maunder, prattle, blab,
         gibber, tattle, blabber, gabble]