kršten

1. baptized; christened
   Dete je kršteno u manastiru. — The child was baptized in a monastery.
   Nije kršten, ali slavi Božić. — He isn't baptized, but he celebrates Christmas.
2. colloq. (in questions and negatives) sane; sensible; in one's right mind
   Jesi li ti kršten? Ko tako parkira? — Are you out of your mind? Who parks like that?
   Taj čovek nije kršten, vozi kao lud. — That man isn't right in the head, he drives like a maniac.

The question Jesi li ti kršten? is a disapproving rebuke meaning 'are you out of your mind?', not a question about baptism.