Halfpipe

A pipe-shaped snow construction which amateur and competitive skiers and snowboarders perform tricks out of as they descend down the hill.
Found on https://gb.ski.com/ski-glossary

Halfpipe

A U-shaped channel with smooth walls used by freestyle skiers and snowboarders for aerial tricks. Typically a halfpipe is created by carving a channel out of massive piles of snow, but they can also be dug out of the ground in areas with minimal snowfall.
Found on http://www.skis.com/Glossary-of-Ski-Terms/article-12-18-2012,default,pg.htm

Halfpipe

U-shaped Ramp.
Found on http://www.encyclo.co.uk/local/21300
No exact match found