Experience or know-how relating to intercourse or other sexual acts. It has to be real-world experience; you can't get it from watching porno or reading erotica.
1: Dude, I'm going over Linda's house.
2: Isn't she your lab partner?
1: Yeah, we're gonna be doing some experiments.
2: Maybe you could talk her into doing some sexperiments.
To have sex with someone just to see what it would be like or for science! Sexperiments may be logged in a journal but they must have a purpose whether it be to see what there vagina looks like or whatever and like all experiments you have to learn something.
George decided to perform a sexperiment on stacey and log the sexperiment in his science composition book.
Jacobs sexperiment was a sucess he had sucessfully figured out the algorithim for ogrewhelming sex with shrek.
