The ability or 6th sense to tell if someone is crazy even if they give no obvious indication that they are crazy.
It's something like the straight lover of Gaydar or like how spiderman has spidey senses. With Crazar you can detect if a person is crazy.
Really good but under appreciated friend: Dude, as a really good but under appreciated friend, there's something about that girl that tells me you shouldn't go home with her tonight. My CRAZAR is going off like a motherf'er.
Player: Man...you're just jealous. I'm gonna get me some booty.
(Later on that evening, Player calls friend)
Player: You were right, that chick is crazy. She has 14 cats and a 3rd nipple. I've never played with so much pussy at once.