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The sexual act of slapping anothers eyes with your testicles.
"Hey Marty did you see Bob's black eyes?"
"Yeah dude, he got the ballseye"
by UPtheNOSEinbetweenTHETOES September 18, 2011
Commonly used to make fun of guys who got hit in the balls, same as in bullseye (right in the spot).
-Wrestler gets kicked in the balls during a wrestling match-

Wrestler: *screams* "ooohhh!!! My balls!!!"
Girls watching the match: Hahaha! ballseye!!!
Wrestler: *cries*
by Roderic storm May 31, 2012
An act whereby one male participant places his testicles inside of a pair of water goggles and then leaves said goggles for the next unfortunate individual who stumbles upon said pair of goggles.
Dude, be careful, you don't know if the last guy left those goggles to ballseye someone!
by Dogbros June 07, 2011