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]