I know what's a sweep but really what is it? Lets say Excadrill took out 4 Pokemon out from the oppenent, is that a sweep or those Excadrill have to K.O all 6 Pokemon for it to be a sweep?
A Sweep is a term to describe knocking out an opposing team's Pokemon easily with just one Pokemon. This can vary from 3 Mons to an entire team really. There is no "general term" to describe a Sweep, it's just one of those things that you know happens.
One of my favorite sweeps.
It's basically when you defeat all six Pokemon of the opponent's Pokemon without any of yours getting defeated. So, for example, 'a 6-0 sweep'.
Hope I helped. :)