otkazivati

1. to cancel; to call off
   Stalno otkazuje sastanke u poslednjem trenutku. — He keeps cancelling meetings at the last minute.
   Zbog snega otkazuju sve letove. — They're cancelling all flights because of the snow.
2. (of a machine, organ) to fail; to break down
   Kočnice su počele da otkazuju na nizbrdici. — The brakes started to fail on the downhill.
   Noge su mi otkazivale posle maratona. — My legs were giving out after the marathon.
3. (of jobs, contracts) to lay off; to terminate
   Mnoge firme ovih dana otkazuju radnicima. — Many companies are laying off workers these days.

The perfective is otkazati; to fire someone is otkazivati + dative (radnicima).