A half pipe (also written halfpipe or half-pipe) is a construct used for snowboarding. It is made of sculpted snow, typically through the use of a specialized machine. One such machine the Bombardier Plus MP, using an optional "Half pipe wing on front blower". It is similar to the typically wooden half-pipe used inskateboarding, save that it is made of snow, much longer, and is placed on a downhill slope, as you cannot kick to gain velocity on a snowboard as you can on a skateboard.
References:
Website: Bombardier (http://www.bombardier.com)