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.
      [1913 Webster]

   2. Noise made by collision of the teeth, as in shivering.
      [1913 Webster]

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.
      [1913 Webster]

   2. To talk idly, carelessly, or with undue rapidity; to
      jabber; to prate.
      [1913 Webster]

            To tame a shrew, and charm her chattering tongue.
                                                  --Shak.
      [1913 Webster]

   3. To make a noise by rapid collisions.
      [1913 Webster]

            With chattering teeth, and bristling hair upright.
                                                  --Dryden.
      [1913 Webster]

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"

Moby Thesaurus II by Grady Ward, 1.0:

185 Moby Thesaurus words for "chatter":
   accents, babble, babblement, bavardage, be cold, bibble-babble,
   blab, blabber, blah-blah, blather, blether, blethers, bob, bobble,
   bounce, brattle, bull, bump, cackle, call, caquet, caqueterie,
   carol, caw, chaffer, chat, chattering, cheep, chill, chirk, chirp,
   chirr, chirrup, chitchat, chitter, chitter-chatter, chuck, clack,
   clacket, clatter, clatter about, clitter, clitterclatter, cluck,
   clunter, cock-a-doodle-doo, comment, conversation, converse, coo,
   croak, cronk, crow, cuckoo, declaim, didder, discourse, dither,
   drag out, draw out, drum, elocution, extend, falter, fill out,
   freeze, freeze to death, gab, gabble, gaggle, gas, gibber,
   gibble-gabble, go on, gobble, gossip, grow cold, guff, guggle,
   gush, have a chill, have an ague, have goose pimples, haver, honk,
   hoo, hoot, horripilate, hot air, hustle, idle talk, jabber,
   jabbering, jactitate, jar, jaw, jog, joggle, jolt, jostle, jounce,
   jump, language, lose heat, mere talk, mouth, natter, never finish,
   nonsense talk, oral communication, pad, palaver, parole, patter,
   peep, perish with cold, perorate, pip, pipe, pour forth, prate,
   prating, prattle, prittle-prattle, protract, quack, quake, quaver,
   quiver, racket, ramble on, rapping, rattle, rattle around,
   rattle on, rattletybang, rattling, reel off, roll, ruckle, run on,
   run out, scold, shake, shiver, shock, shudder, sing, small talk,
   speak, speak at length, speaking, speech, spin out, spout,
   spout off, squawk, stretch out, string out, stultiloquence, talk,
   talk away, talk nonsense, talk on, talkee-talkee, talking,
   tittle-tattle, tremble, trill, twaddle, twattle, tweet, twit,
   twitter, vibrate, waffle, wag the tongue, warble, whistle, wobble,
   words, yak, yakkety-yak, yakking, yammer