The Collaborative International Dictionary of English v.0.48:

shop talk \shop talk\,
   conversation about a matters pertaining to person's
   occupation; -- often used of such discussions when conducted
   outside of working hours, as in social gatherings.
   [PJC]

WordNet (r) 3.0 (2006):

shop talk
    n 1: talk about your business that only others in the same
         business can understand