From Longman Dictionary of Contemporary EnglishACASACAS /ˈeɪkæs/ (Advisory Conciliation and Arbitration Service) a British organization that tries to end disagreements about pay, conditions at work etc between the management of a business and its workersFrom Longman Business DictionaryACASACAS /ˈeɪkæs/ nounORGANIZATIONS Advisory, Conciliation and Arbitration Service; a government organization in Britain that attempts to solve disagreements between employers and employeesUnder terms agreed with ACAS, both sides have agreed not to comment during negotiations.