The Collaborative International Dictionary of English v.0.48:

Chatter \Chat"ter\, n.
   1. Sounds like those of a magpie or monkey; idle talk; rapid,
      thoughtless talk; jabber; prattle.
      [1913 Webster]

            Your words are but idle and empty chatter.
                                                  --Longfellow.
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   2. Noise made by collision of the teeth, as in shivering.
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The Collaborative International Dictionary of English v.0.48:

Chatter \Chat"ter\, v. i. [imp. & p. p. Chattered; p. pr. &
   vb. n. Chattering.] [Of imitative origin. Cf. Chat, v. i.
   Chitter.]
   1. To utter sounds which somewhat resemble language, but are
      inarticulate and indistinct.
      [1913 Webster]

            The jaw makes answer, as the magpie chatters.
                                                  --Wordsworth.
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   2. To talk idly, carelessly, or with undue rapidity; to
      jabber; to prate.
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            To tame a shrew, and charm her chattering tongue.
                                                  --Shak.
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   3. To make a noise by rapid collisions.
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            With chattering teeth, and bristling hair upright.
                                                  --Dryden.
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The Collaborative International Dictionary of English v.0.48:

Chatter \Chat"ter\, v. t.
   To utter rapidly, idly, or indistinctly.
   [1913 Webster]

         Begin his witless note apace to chatter. --Spenser.
   [1913 Webster]

WordNet (r) 3.0 (2006):

chatter
    n 1: noisy talk [syn: yak, yack, yakety-yak, chatter,
         cackle]
    2: the rapid series of noises made by the parts of a machine
       [syn: chatter, chattering]
    3: the high-pitched continuing noise made by animals (birds or
       monkeys) [syn: chatter, chattering]
    v 1: click repeatedly or uncontrollably; "Chattering teeth"
         [syn: chatter, click]
    2: cut unevenly with a chattering tool
    3: talk socially without exchanging too much information; "the
       men were sitting in the cafe and shooting the breeze" [syn:
       chew the fat, shoot the breeze, chat, confabulate,
       confab, chitchat, chit-chat, chatter, chaffer,
       natter, gossip, jaw, claver, visit]
    4: speak (about unimportant matters) rapidly and incessantly
       [syn: chatter, piffle, palaver, prate, tittle-
       tattle, twaddle, clack, maunder, prattle, blab,
       gibber, tattle, blabber, gabble]
    5: make noise as if chattering away; "The magpies were
       chattering in the trees"