Star Spin is a move that Mario can perform in Super Mario Galaxy. It is done with the Wii Remote when the player shakes the Star Cursor around the screen. The move is slightly like a Spin Jump on the ground. It can be used to hit objects thrown at Mario to launch them back, activate Boost Stars, even pummel enemies and dig up coins.
A very useful technique of the Star Spin is the ability to stun/freeze enemies by whipping the Star Cursor at them. This gives Mario a chance to run away or attack the enemies if the Player is fast enough.