The uncanny ability of a junkie/drug user to locate substances at any given time or location
Billy's junkdar struck again: we were having a good time at the bar and next think you know he's got an eight-ball. He ruined another 'beer only' night with his junkdar.
A unique attribute of the female gender and gay males; a sense that seeks out a man’s penis as if guided by radar.
Erin's junkdar was honing in on Casey. She really wanted some action and nothing was going to stop her.