What is an antenna in volleyball?

Answer 1

In volleyball, there is an antenna. It is there to mark the place of the "out of bounds" line on the court. If the ball ever hits the antenna, the ball is "out of bounds".

Answer 2

The antennae in volleyabll is an extention of the net. It allows for the referee to make a better judgement as to whether a ball is in our out of play while in the air and crossing the net.