What does volly mean in volly ball?
A volley is when a player obstructs the ball if he, or anything
he wears or carries, touches the ball in play when it is above or
travelling towards the playing surface, not having touched his
court since last being struck by his opponent.
So, very simply, a volley is when a player hits the ball before
it bounces on his side of the table. This is not allowed.