Flight Closed  is when you see your flight flashing "Closed" you have missed your flight. 
 Once a flight has Closed, the  door is shut, the  Gate Agent is standing at the  end of the  Jetway steering it away from the  aircraft so it can 'push back.'
 
Other definition:
Flight Closed is when you see your flight flashing "Closed". You have missed your flight. Once a flight has Closed, the  door is shut, the  gate agent is standing at the  end of the  Jetway steering it away from the  aircraft so it can 'push back.'     
        
                                        