The Screw Attack (スクリューアタック, Sukuryu Atakku) is a moved used by Samus Aran by pressing Up-B. The move shoots Samus into the air and spins her around and around, inflicting damage on any opponents that touch her. It's also often used to survive from a fall off the stage.
The Screw Attack is one of the last special abilities Samus can learn, causing her to spin with electrical energy whenever she jumps. Combined with the Space Jump, Samus can continually jump and destroy everything in her way.
Unfortunately, in Super Smash Bros. Melee, any charging of your Charge Shot will be cancelled if you are hit during this attack in the PAL version of the game.