Referee's Signal Number 10 - Various Meanings
This signal is used in a number of circumstances:
Begin the motion with both hands in front of your chest and expand them out to full extension to the side keeping them parallel to the ground in an unhurried manner. Repeat a couple of times. Do not lean forward (a common mistake) when giving this signal. Make sure you do not hit anyone when making this signal (it hurts!).
If giving this signal for types 4-6 above, it should be accompanied or preceded by a loud blast on the whistle. If you are the on-field timekeeper, stop the watch if necessary before making the signal. Also ensure that the Referee has noticed your signal - he will then turn and confirm the no-score by making the same signal to the press-box.