indirectly (through the use of clever words or space/time paradoxes) stopping a friend from getting laid or finishing the sex, if he does get laid.
You: Dude, you should jerk it before she comes over tonight, just in case you get laid. She'll think you last longer!
*friend, later that night after jacking off: sex lasts so long parents interrupt, meaning he couldn't finish*
Friend: Damn, he totally spockblocked me!
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi