As a Noun: 1. Behaviour which is unkind and unpleasant. English = nastiness. 2. Someone who behaves in a very unpleasant way. English = bitch. As a Verb or Adjective: 1. Of behaviour, to be unkind and unpleasant. English = (be) nasty, (be) mean. 2. To be very unpleasant to see, experience or feel. English = (be) nasty. 3. To complain or talk about something or someone in a nasty way. English = bitch