In
skateboarding it is the way you enter a
halfpipe (or come down from the top of a
quarterpipe).
Stand at the edge of the pipe with your tail on the coping (back foot on the tail, the other foot off the board). Do not take time to steel yourself or look down if it is your first time, because it will only scare the shit out of you. Resist the urge. Simply put your front foot back onto the board (above the deck bolts) and lean forward and continue to lean forward the whole way.
Once you get good at doing this you can slide your foot off the tail once you get to the flat. This means you will fall less (but if you try it when you are not good it means you will fall more).