One who debates from a view which they may not actually hold, usually to determine its validity, or simply for the sake of argument
(Roman Catholic Church) A canon lawyer appointed by the Church to argue against the canonization of the proposed candidate
If you play devil's advocate in a discussion or debate, you express an opinion which you may not agree with but which is very different to what other people have been saying, in order to make the argument more interesting. someone who pretends to disagree with you in order to have a good discussion about something