junačiti

1. derog. (junačiti se) to act tough; to show off one's bravery
   Nemoj da se junačiš, znam da se bojiš. — Stop acting tough, I know you're scared.
   Junačio se pred devojkama, a onda pobegao. — He was showing off in front of the girls, then ran away.
2. formal (+ acc.) to encourage; to embolden
   Komandant je junačio vojnike pred bitku. — The commander was encouraging the soldiers before the battle.

It is mostly used reflexively, as junačiti se.