terrain park

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A ski trail or section of a ski trail that contains objects, such as ramps, rails, and quarterpipes, that are used to perform tricks while on skis or a snowboard.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An area in a park type setting, often within a ski resort, designed for snowboarding or sometimes skiing and typically containing features such as ramps and rails for sliding on.