poligon

1. training ground; range; driving test ground
   Sutra imam ispit na poligonu u auto-školi. — Tomorrow I have my test on the driving school's training ground.
   Vojnici su vežbali gađanje na poligonu. — The soldiers practised shooting on the range.
2. (in geometry) polygon
   Nacrtaj pravilan poligon sa šest stranica. — Draw a regular polygon with six sides.
3. (figuratively) testing ground; arena
   Društvene mreže su postale poligon za političke obračune. — Social media have become an arena for political fights.

In school geometry mnogougao is more common for "polygon".