At certain locations when a player steps near a wall and jumps to it she/he will end up "sticking" to the wall in mid-air. Now the player can perform a speed-gaining technique like strafe-jumping without her/his character moving from the spot, but "accelerating" nevertheless. This is a real anomaly as the player character does not move in gamespace, but the game engine ascribes ever higher speed to it. The player then can "unstick" from the wall by firing a splash damage weapon into it, and subsequently will move with the speed gained "on the spot". This technique is called "sticky wall" or "rebounce".