Basically, you position yourself to deal with them one at a time and, what I think, is that you aim to go right through them, just like Ellis was explaining with the sword = irimi. Think about it. If you are surrounded by ten mad samurai like in the movies the only thing you can do is cut them all - one at a time. You won't have much time to avoid anything at all. In fact, even the tiniest avoidance will be the death of you - you have no time at all for defence.
Sounds okay... but what about those videos of O-Sensei where he's surrounded by a bunch of guys with swords who all strike him at once? Certainly he's not dealing with them one at a time. Is the movement he makes irimi or tenkan? How do you irimi ten guys on all sides of you?