Aporime
（重定向自Apore）
An aporime is a problem difficult to resolve, and which has never been resolved, though it may not be, in itself, impossible.
The word is derived from the Greek ἄπορον, which signifies something very difficult and impracticable, being formed from the privative α, and πόρος, "passage". When a question was proposed to any of the ancient Greek philosophers, especially of the sect of Academists, if he could not give a solution, his answer was ἀποροῶ, q.d. "I do not conceive it; I cannot see through it; I am not able to clear it up."