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1.
When your initial assumption about the level of attractiveness of any given girl in tights, from the back, is proven drastically wrong when she turns around and reveals she is actually a grenade.
Guy1: Dude, look at that girl and her tights. She's so hot.
Guy2: Nah dude, she's a trojan grenade. Wait for her to turn around.

Girl1: Ugh, and she looked so good from the back...
Guy1: Yeah, that's a trojan grenade.
by Anti-Buzzkill Laws March 07, 2011