شیطان / sheytoon / mischievous
Sheytoon also means devil, but when you call someone sheytoon it simply means mischievous or naughty. "My niece is very quiet and calm, but my nephew is becoming more and more sheytoon."
Iranians often also use this word almost as a term of endearment. I was calm and easy-going as a child, but on the occasion that I would say something clever or funny, my uncle would laugh and say "Ay sheytoon!"
Years ago, I even saw a license plate that said: Sh82n. Doesn't look like nonsense anymore, does it?
Check out the classic song Sheytoon Bala from the beloved singer Andy. This is the first time I've seen the video, and I'm not quite sure what's going on, but oh how the song brings back memories...