In alpine skiing, a fall line refers to the line down a mountain or hill which is most directly downhill. That is, the direction a ball would roll if it were free to move on the slope under gravity. A skier is said to be "skiing the fall line" if he is skiing a line with his skis pointing generally down, rather than traversing across it.
Fall-Line Analysis: An evaluation of the mountain terrain in terms of the natural fall-line. The fall-line is the path an object takes as it moves down a slope perpendicular to the contour lines. Fall-line skiing provides for the natural flow of skier routes which will serve all skier ability levels, from the top of the mountain to the base areas, on a consistent basis. Consistency of fall-line provides the best recreational skiing experience with the least amount of environmental disruption due to minimal requirements for earthwork during ski trail construction.