(adj.) A JANKY person is your friend, while secretly stealing everything you own in a sneaky manner: such as your wallet, drugs, girl friend, or anything in sight left unattended.
"I woke up and all my shit was gone! That JANKY fucker even stole the shoes off my feet!"
"I couldn't find my dope anywhere, and that JANKY Johnny helped me look for it! Come to find out he had it in his pocket the whole time yet still helped look for it, that sneaky bastard!"