Vectoring
Vectoring refers to the manner in which Mario's fall speed is maximized by moving at an angle that is 45 degrees apart from the direction in which the fall was initiated.
When Mario jumps (does not apply to long jumps), vaults, rolls, roll cancels or falls off the edge of a platform with momentum, the game keeps track of the direction in which his jump or fall was initiated. Mario's fall can be vectored by moving in any direction that is diagonal from this initial direction (45, 135, 225 or 315 degrees).