کس‌خل

Kos-khol is the textbook case of register-flexible profanity. The word's literal meaning never disappears, but the social transaction overrides it in close-friend contexts. A Tehrani twenty-something can say "kos-khol-i to" ("you're nuts") to a friend who just made a stupid joke and have it land as warm. The same line said to a stranger crossing the street starts a different kind of conversation.