(pɑːˈkʊə(r)): n.  A sport or athletic activity in which the participant seeks to move quickly and fluidly through an area, often an urban locale, by surmounting obstacles such as walls and railings and leaping across open spaces, as in a stairwell or between buildings.

As an ex-acrobat, I find that ‘normal’ sports don’t offer me the challenge I need to keep sharp, both physically and mentally.  So I challenge myself against the environment.