Disc Jumping is a technique used in Tribes Ascend to increase a player's speed. Players will turn (skiing backwards) and fire an explosive weapon at the ground between a 45-75 degree angle and jetpack simultaneously. The angle of fire depends on the angle of the ground. On a near flat surface a 45 degree shot will give a player more horizontal acceleration, when skiing up a slope a steeper angle such as 55-75 is needed to create diagonal acceleration.
Traversing maps quicker is not the only benefit, a player can fire straight down just after reaching the top of a slope will receive a vertical acceleration to clear large obstacles and reach areas that would be inaccessible with normal jetting.
All classes with explosive weapons can disc jump. Lighter classes will gain significantly more speed, but heavier classes have more health to spare.