The reflection of an unlit computer screen after it is accidentally or unwillingly shutdown while you're in front of it, giving you a chance to rethink your life as you see your self.

Condition which causes you to place an Amazon order, then shortly after remember something else you needed and place another order.

When you're jerkin' it to some weird shit and your computer shuts off, leaving a black screen reflecting just your face.

To 'black mirror' someone - is to block/'mute' them across all possible contact and social channels (e.g. Facebook, email, phone, text, blogs, etc.) and delete any evidence of a prior relationship either party- as per the Black Mirror 2014 Christmas Special. Well harsh.