By analogy with sunblock and sunscreen (assuming sunblock deflects the sun's rays and sunscreen absorbs them), a cockscreen does not block cock, she absorbs it. Thus, you are not completely blocked from the friend, but may have to sleep with the cockscreen first to get through.
"That girl Dana there is being a total cockblock for her hot friend Jennifer!"
"Nah, she's just a cockscreen. Give her some lovin' and you'll get through, trust 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
May I have an order of regular degular buttermilk pancakes? Without all the added jazz? Hold the blueberry smiley face, strawberry glaze, chocolate chips and whipped cream.