Gordian knot

гордиев узел

Большой англо-русский словарь

Gordian knot

noun 1. an intricate problem; especially a problem insoluble in its own terms — often used in the phrase cut the Gordian knot 2. a knot tied by Gordius, king of Phrygia, held to be capable of being untied only by the future ruler of Asia, and cut by Alexander the Great with his sword

Merriam-Webster's Collegiate Dictionary