Longman Dictionary of Contemporary English - theoretically

~ adv sentence adverb 1 used to say what is supposed to happen in a particular situation when the opposite is true  (Theoretically, Damian's the boss, but I co-ordinate the team on a day-to-day basis.) 2 according to a scientific idea that has not been proved to be true in a practical way  (It is theoretically possible for computers to be programmed to think like humans.)