smanjivati

1. to reduce; to decrease; to cut
   Vlada postepeno smanjuje troškove. — The government is gradually cutting costs.
   Uvek smanjuj brzinu pred raskrsnicom. — Always slow down before an intersection.
2. (smanjivati se) to decrease; to shrink; to decline
   Broj stanovnika u selu se stalno smanjuje. — The village's population keeps shrinking.

The perfective is smanjiti.