Sheriff Stilinski: "So you lied to me?"
Stiles Stilinski : "That depends on how you define lying."
Sheriff Stilinski: "Well I define it as not telling the truth. How do you define it?"
Stiles Stilinski: "Reclining your body in a horizontal position."
I common phrase used in Ireland. It is basically the shortened version of "Why are you lying for? or "What are you lying for? It is usually used in a Rhetorical manner.