The definition probably originates from the 1990s. But think about it, extreme sport has probably been around as long as man himself.
Take, for example, Harry Houdini. He definitely was an extreme sport kind of man. We had a bird named Houdini a few years ago. For some reason, he always got out of the cage, even though the door was shut. He also liked to fly like the Red Baron into the flames of lit candles on the dining room table.
Stunt performers are the same - wild and crazy, loving adreanalin kicks and audacious exitement.
My son has tried quite a few different things, but is smart enough to tell his mother afterwards - he knows I would worry too much, if I knew of his adventures ahead of time.
One thing is certain, extreme sport takes you outside your comfort zone - much higher, further, steeper, crazier than normal. But what is normal anyway.