When someone is there next to you and a moment later they disappear (or appear, if they weren't next to you). When that happens, you get ghostface'd.
Girl: How did you get in here?
Boy: I thought you saw me.
Girl 2: Haha, he ghostfaced ya, hon!
_______________________________________
Boy: Man, I'm so bored, aren't y......where the hell are you? Damn I got ghostface'd!
2👍 4👎