missionary UK /ˈmɪʃ.ən(ə).ɹɪ/US /ˈmɪʃ.əˌnɛɹ.ɪ/noun 5adjective 1forms 1 noun5 •One who is sent on a mission. •A person who travels attempting to spread a religion or creed (Particularly used in context of Christianity).A missionary was just trying to convert me to his religion. •A religious messenger. •(informal) The missionary position for sexual intercourse.My boyfriend only cums during missionary. •(slang) Sexual intercourse in the missionary position. adjective1 •Relating to a (religious) mission. formsmissionaries