sumanut

1. crazy; insane; mad
   To je sumanuta ideja, nikad neće uspeti. — That's a crazy idea, it will never work.
   Vozio je sumanutom brzinom kroz grad. — He drove through the city at an insane speed.
2. (of a person) deranged; frantic
   Trčao je kao sumanut kroz hodnik. — He ran down the corridor like a madman.

More often used of ideas, plans and actions than of people.