cl_mouseaccel

cl_mouseaccel is a setting which can enable or disable the acceleration of the mouse in the game.

Usage:
/seta cl_mouseaccel 0

Values: “1” or “0”

Note:
However if the driver of your mouse have acceleration enabled, the mouse will still have acceleration turned on.
Mouse acceleration: when you move your mouse constantly starting from a point (for example from the middle of your screen toward right), it will move faster while getting further and further from the starting point.