noun, noun or participle which takes 'suru', intransitive verb
religious mission; religious proclamation
Refers to spreading a religious faith, often used in Christian contexts but applicable to any religion. Can be used as a noun or with する to mean 'to do missionary work'.
彼は海外で宣教活動をしている。
He is doing missionary work overseas.
キリスト教の宣教は世界
Christian missionary work is carried out all over the world.