n.1 a person guilty or capable of great wickedness.
2 colloq. usu. joc. a rascal or rogue.
3 (also villain of the piece) (in a play etc.) a character whose evil actions or motives are important in the plot.
4 Brit. colloq. a professional criminal.
5 archaic a rustic; a boor.
Etymology: ME f. OF vilein, vilain ult. f. L villa: see VILLA