mlaz

1. (of liquid, gas) jet; stream; spurt
   Iz slavine je pokuljao jak mlaz vode. — A strong jet of water gushed from the tap.
   Krv je šikljala u mlazu. — The blood was spurting out.
2. (of light) beam; shaft of light
   Kroz prozor je ulazio mlaz sunčeve svetlosti. — A beam of sunlight came in through the window.

The adjective "mlazni" comes from it: mlazni avion "jet plane".