Audience wave

A packed crowd in a stadium does the wave (in some places outside of North America known as the Mexican wave) when a wave is created in the crowd by successive groups of spectators briefly standing and raising their arms. Each spectator is required to rise at the same time as those straight in front and behind, and slightly after the person immediately to either the right (for a clockwise wave) or the left (for a counterclockwise wave). Immediately upon stretching to full height, the spectator returns to the usual seated position.
See more at Wikipedia.org...