When you get set up to let your guard down and get robbed, usually by a girl who fakes interest in you so that you stay in one spot and she can give your location to whoever wants to harm you.
Marc: I heard Bennett got lined by Alicia, they kicked down his door and ran his pockets!
Bennett: Alicia lined me, I can never trust a thot ever again.
Refers to the chalk line drawn around a corpse in movies. The 'line' idea is mostly fictional, since it contaminates the crime scene investigation, but it serves as more dramatic metaphor for murder.
You better watch how you're talking and where you're walking, or you and your homies might lined in chalk. (Coolio - Gangsta's Paradise)