Backpack Boner
Where a kid has so many books in their backpack, to the point where you are able to see the books protruding out. This look is often sported by the nerds of your school
Tom: "Whoa, look at that kid, his backpack is so full!"
Bill: "Yea, he has one gnarly backpack boner."
Bill: "Yea, he has one gnarly backpack boner."