revolver fanning
A shooting technique for single-action revolvers in which one holds down the trigger in one hand, and uses the other to hit the hammer singularly or repeatedly without any part of the cocking hand remaining in contact with the revolver or support hand. This rotates the cylinder and fires the weapon, allowing for rapid fire.
Popularized by western films, it is widely considered to be inadvisable for use in real-life firefights, as it provides no tactical benefit to speak of.