Fall-Line

It’s direction a ball travels if released to roll freely downhill.  Skis pointed downhill, and placed flat on the snow, will slide straight down the fall-line.  If you’re traversing across the slope, or finishing a turn,  and roll your skis off edge they will seek the fall-line.   Skiing down the fall-line results in an increase in speed.  By turning, a skier exits the falline and manages speed.

Need video here