When you and a member of opposite sex work on the same greasy mechanical project before hooking up. Mingling the same greasy hands on one anothers body.
When you leave a handprint on her ass after a little Fort Mac Foreplay, it's not red from snacking it. It's black.
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