1. Someone who gains pleasure from watching, especially secretly, other people's bodies or the sexual acts in which they participate; especially from a secret vantage point.
2. A persistent observer of misery or scandal; a fascinated observer of distressing, sordid, or scandalous events.
3. Etymology: a scopophiliac (someone who derives sexual pleasure by looking at nude bodies, erotic photographs, etc.), from 1900, from French voyeur (1898); literally, "someone who views or inspects", from French voir, "to view", from Latin videre, "to see".