The Collaborative International Dictionary of English v.0.48:

Natter \Nat"ter\, v. i. [Cf. Icel. knetta to grumble.]
   1. To find fault; to be peevish. [Prov. Eng. or Scot.]
      [1913 Webster]

   2. To talk constantly; to chatter incessantly to prattle; as,
      nattering like a chatterbox.
      [PJC]

WordNet (r) 3.0 (2006):

natter
    v 1: 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]

Moby Thesaurus II by Grady Ward, 1.0:

59 Moby Thesaurus words for "natter":
   babble, babblement, bavardage, bibble-babble, blab, blabber,
   blah-blah, blather, blether, blethers, cackle, caquet, caqueterie,
   chat, chatter, chitter-chatter, clack, clatter, dither, gab,
   gabble, gas, gibber, gibble-gabble, go on, gossip, guff, gush,
   haver, hot air, idle talk, jabber, jaw, mere talk, nonsense talk,
   palaver, patter, pour forth, prate, prating, prattle,
   prittle-prattle, ramble on, rattle, rattle on, reel off, run on,
   spout, spout off, talk away, talk nonsense, talk on, talkee-talkee,
   tittle-tattle, twaddle, twattle, waffle, yak, yakkety-yak