opravdati

1. to justify; to excuse; to vindicate
   Ništa ne može da opravda takvo ponašanje. — Nothing can justify that kind of behaviour.
   Ne pokušavam da ga opravdam, ali bio je pod velikim pritiskom. — I'm not trying to excuse him, but he was under a lot of pressure.
2. (expectations, trust) to live up to
   Novi trener je opravdao očekivanja navijača. — The new coach lived up to the fans' expectations.
3. (of an absence) to excuse
   Doneo je potvrdu od lekara da opravda izostanke. — He brought a doctor's note to excuse his absences.
4. (opravdati se) to justify oneself; to make an excuse
   Pokušao je da se opravda, ali mu niko nije verovao. — He tried to justify himself, but nobody believed him.

The imperfective is opravdavati or pravdati.