Definitions by Cohen, Baluch and Duffy 2018

Extreme Sport 

A predominantly competitive (comparison or self-evaluative) activity within which the participant is subjected to natural or unusual physical demands. Moreover, an unsuccessful outcome is likely to result in the injury or fatality of the participant, in contrast to non-extreme sport. -Cohen, Baluch and Duffy

Base Jumping is an extreme sport which is very dangerous and risky though very exciting .

Extreme Sport by Cohen, Baluch and Duffy 2018 October 31, 2018