2) A children's Book from the '60's from which the term got it's name.
1) I was sitting in math and got a major flat stanley.
2) Hi flat stanley, do you wanna come out and play?
Guy 1- Dude she's hot I would bang her.
Guy 2- No way dude did u see her ass??
Guy 1- No I didn't.
Guy 2- Exactly cuz she's a flat stanley.
(Girl slips through crack in locked door, leaving the rest of the party to wait outside)
Student: Damn she's such a flat stanley.