podgrejati

1. (of food) to reheat; to warm up
   Podgrej supu u mikrotalasnoj, ohladila se. — Heat the soup up in the microwave, it's gone cold.
   Podgrejala sam ručak od juče. — I reheated yesterday's lunch.
2. (of feelings, disputes) to fuel; to intensify; to rekindle; to stir up again
   Ta izjava je samo podgrejala stari sukob. — That statement only stirred up the old conflict again.
   Pokušali su da podgreju staru ljubav, ali nije uspelo. — They tried to rekindle their old romance, but it didn't work.

The imperfective counterpart is podgrevati.