smejanje

1. laughing; laughter
   Iz susedne sobe čulo se glasno smejanje. — Loud laughing could be heard from the next room.
   Prestanite sa smejanjem, ovo je ozbiljna stvar. — Stop laughing, this is a serious matter.

This is the verbal noun of smejati se and refers to the act of laughing; for laughter in general, smeh is more usual.