Any individual who can bring about chaos in an otherwise pleasant situation. The Sith is generally surrounded by 165 mile per hour winds and no less than 30 minions. The Sith is not to be underestimated as his/her vortex of evil energy can tear down buildings, train tracks, and engulf entire universes.
Sam: "What a beautiful day it is today."
Sara: "Not a cloud in the sky, so peaceful."
Sam: "Look at that asshole over there throwing rocks at children and pissing on that Jesus statue.
Sara: "That asshole is a real piece of SITH."