pravdati

1. (with se) to make excuses; to justify oneself
   Nemoj da se pravdaš, samo priznaj grešku. — Stop making excuses, just admit your mistake.
   Stalno se pravda šefu zbog kašnjenja. — He keeps making excuses to his boss for being late.
2. (+ acc.) to justify; to excuse
   Ništa ne pravda takvo ponašanje. — Nothing justifies that kind of behavior.
   Mora da pravda izostanke lekarskim opravdanjem. — He has to excuse his absences with a doctor's note.

The person you make excuses to is in the dative: pravdati se nekome.