steg

1. formal banner; standard
   Na čelu kolone vijorio se crveni steg. — A red banner fluttered at the head of the column.
2. formal flagpole; flagstaff
   Zastava je podignuta na visoki steg. — The flag was raised on a tall flagpole.

In everyday speech zastava or barjak is more usual; stegonoša "standard-bearer" comes from steg.