Top Definition
The phenomenon of increasingly rare and awkward instances of hooking up, making out, having sex, etc. that occurs primarily within small high schools where many of the students have grown together since birth. The reason being is that everyone has a pre-determined judgement of each other as well as viewing their fellow classmates as pseudo-siblings. To most people, the thought of hooking up with your sibling is a repulsive thought and therefore hooking up with a pseudo-sibling is equally disturbing. However, due to the lack of available mates, the students must commit the act of coitus or become pent up in their sexual frustration.
Example 1:

Rodolfo: Sup dude, I'm gonna try to hook up with Lauren at the kegger.

Alex: Dude you've known her since you were in pre-school, that shit ain't happening.

Rodolfo: Yeah you're right. Fuck High School Incest!

Example 2:

Heidi: I think I fucked Tony last night...

Serena: You redneck! You committed High School Incest!

Heidi: Not again!
by 12ssmalanskas September 10, 2011

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