This is is a reel of the exploits of wingsuit BASE jumper Jeb Corliss, sailing over cliffs, mountains, trees, valleys, and the statue of Christ the Redeemer in Rio. This is the sort of thing Garreth likes to get up to in his free time, apparently.
From Spook Country:
"What did you do, Garreth, before you started doing whatever this is that you’re doing now?"
He considered. “Extreme sports. Some hospital, as a result. Fines and a little jail, likewise. Built props for films. Did stunts for them as well. And what did you do, between ‘Hard To Be One’ and what you’re doing now?”
"Did badly in the stock market. Invested in a friend’s music store. What do you consider ‘extreme’ sports?"
"BASE jumping, mainly."
"Acronym. B building, A antenna, S span, as in bridge, arch or dome, E earth, a cliff or other natural formation. BASE jumping."
From Zero History:
The old man would not, Hollis imagined, have approved of their involvement, but the multiskilled Garreth would have been impossible to replace. A man whose idea of fun was to fling himself off skyscrapers in a nylon suit with airfoil membranes sewn between the legs, and arms-to-thighs; a human flying squirrel, amid lethally unforgiving uprights of glass and steel.