From Longman Business Dictionaryclassification societyclas‧si‧fi‧ca‧tion so‧ci‧e‧ty British English /ˌklæsəfəˈkeɪʃən səˌsaɪəti/, , classification authority American English noun [countable] INSURANCE an official organization that is responsible for making sure that ships are as safe as possible and for putting ships into classes according to their safetyShipbuilding contracts invariably say that the ship must comply with the rules of the relevant Classification Society.