Pyramid is the pastime of the Twelve Colonies with no other major sport to compete with that title (both because they never mention any other sport and because of the sheer prominence with which it is shown)
Pyramid is a team game of agility, skill, and strength. The game is a bit of a hybrid of many sports most notably basketball. The layout of the court, players "boxing out" and "checking up", and of course simply "shooting" are all similar. The major differences include: the nets are oriented differently (horizontal instead of vertical); both nets and ball are smaller; the shape of the court is different; instead of dribbling, players can only take three steps before passing, shooting or bouncing the ball from a wall (yes, use of walls so no out-of-bounds); and the game is more physical akin to lacrosse or even rugby.
Court sizes can apparently vary from large stadium arena sized to small "backyard" courts that can sometimes even spring up inside a ship.