Proper noun
the barber paradox
A paradox of self-reference, where, supposing that every man either shaves himself or is shaved by the barber, and the barber shaves all and only the men who do not shave themselves, then it is impossible to determine who shaves the barber.
Applications and related topics Russell-like paradoxes As illustrated above for the Barber paradox, Russell's paradox is not hard to extend. Source: Internet