administrator

1. administrator; office clerk
   Administrator u školi mi je izdao potvrdu. — The school administrator issued me a certificate.
2. (in IT) administrator; admin
   Javi se administratoru ako ne možeš da se uloguješ. — Contact the administrator if you can't log in.
   Administrator grupe je obrisao tvoju poruku. — The group admin deleted your message.

In IT, the colloquial short form is "admin".