That's dictionary.com, Lazlo. They do general definitions, not specific nerd-talk.
How degree's of movement in games are defined as the amount of directions you can move in. Mario Kart and F-Zero are two, because, well, left and right. Notice that the ground you're driving on gives no sensation of going up? It looks like a flat plane? It would be four degree's of movement if it did go up. (left, right, up down. The most common for older-newer racing games)
Most FPS's like Unreal Tournament and Halo are 8 degree's of mocement, since you can move up, down left, right, and the diagonals. Descent is 360 degree's of movement, since you can move in ANY freaking direction you want. ANY. Up, down, left, right, forward, backwards, turn left while sliding up, turn right while sliding right, fire lasers while sliding down and turning up, it's all good.
THAT is why I love Descent so much. The freedom of movement is just... astounding. Sure, the 8 degree's of movement in Privateer is good, but.... It's not Descent....
Holy spit, there's more nerd-ism's in there than I care to know.