It means that the rifle's action is capable of cycling 800 times in 1 minute. This is most applicable to full auto mode, which in 2 seconds would mean that you could shoot ~26 rounds.
But it is not inconceivable to shoot 12 times in semi-auto in 2 seconds.
Try this excersie: Just pretend that you are squeezing a trigger and then letting go just enough for what the trigger would need to reset. On an AR the trigger pull is not that long. Then time yourself for 2 seconds. You should be able to make it 10-12 times in 2 seconds. But like I said, you would not be that accurate because you are not compensating for recoil.
I have shot like this in real life on live fire ranges when we had to "expend all remaining ammo" I could unload a mag faster in semi than my friend could on burst.
I am not saying that it is advantageous to do this, and that someone without training "could put 12 slugs in a cops chest in 2 seconds", but it is mechanically possible.