That is a command that they have hacked from the console. It is called Noclip. I have seen it multiple times by hackers. Imagine yourself as a free-form object. You can go in any position horizontal or vertical. Just by looking in the direction and moving forward with 'w'. You can also pass through objects as if you didn't have any collision physics. So they can use this in tandem with a speedhack to kill an entire team the
second they spawn.
I've seen the members of **** using this cheat. You probably can't see the name of the clan but it's the derogatory slang for a homosixual.