arbitrationist|ɑːbɪˈtreɪʃənɪst| [f. arbitration + -ist.] One who is in favour of arbitration. 1884Pall Mall Gaz. 24 June 3/1 Fine doctrine this for the arbitrationists!1902Q. Rev. Oct. 667 As an arbitrationist, he has been a hero with the emotional Radicals.