Epithet for a man who has sex with other men, or sexually assaults other men, but only while in jail, prison,or a similar institution. Calculated to offend the frequent homophobia of such men, who are often closet cases in violent denial.
He made a grab for the new kid who'd been dancing around and looking too happy. So I said, "You inside homosexual, you lay off him, he doesn't know any better." Had to fight him, but it was worth it.