Trichording is the ultimate skill in a 6DoF world. It's compairable to straferunning, Where if you move forward at X speed, and you also move to the side at the same X speed, then if you go both forward and to the side, you straferun, allowing your top moving speed to be ultimately faster than if you just went forward.
Now you could talk about this in a realistic sense, because it's physically possible in real life, however our current technology (at least that which is commercial or feasible) doesn't allow for us to consider this a practice. I'm sure in the future this will be as common as is drifting to cars, but until we move like this we'll have to talk about it in video games.
When I first started playing Descent, I didn't know anything about tricoording, So my controls were pretty standard. I played the game the first time just with backwards and forwards as movement controls. The I played multiplayer and hated multiplayer because I epically failed. So then I started getting tips, like sliding in more directions to escape certain attacks. So the second time I played I added the S anc X Up/Down controls to my current configuration. Then I learned what an advantage trichording was and took my time developing my tricoording skills. So basically if you move 1x speed in the X axis, then you move 1.4x speed with X/Y axis, and about 1.7x speed in all X/Y/Z axis. This should explaing it better than I did...http://en.wikipedia.org/wiki/Strafing_(gaming) Why I use two spellings? I think I'm the only one I've ever seen type it two different ways, but I do this because each word has a different meaning to me.
Trichording (Verb/Noun) - 1) The act of moving(chording)and rotating in three axis at once. 2)The ability to physically chord in three axis. (singular, to trichord)
Tricoording (Adj/Adv) - 1)The controling or ploting of coordinates in three axis. 2)The ability to manage chording and rotating in three axis at once at all times.
Thus in Star Trek, those 'trichorders' are actually Tricoorders. Because they plot and scan the area around them on a 3 axis level. And don't actually manipulate movement in any way. However I could see how the mistake was made when the word was made.
I have a video of Descent 3 multiplayer combat, CTF more precisely showcasing both of these tactics. I start getting in the zone around when the music hits. You'll notice how I make use of all my axis and when i'm going 'straight' i'm somewhat looking at the ground a bit to compensate for the angle of inertia i'm causing. I do ok considering I have 200 ping to Germany :D