[He looks around, careful about who could be listening. He doesn't know this girl, except that she's some kind of hunter and he's just about sent her off to hunt demons of all things. Smart Dean. Next time why don't you gift wrap her and put her in a pink bow? Meg could use her as her next meatsuit.]
It's symbol you paint or carve onto a surface that traps a demon when they walk into it. Like a demon-sized mousetrap.