1. To physically attack one, as with punches and other blows, such that they suffer significant injury. I'm worried that the captain of the football team will clean the floor with me if he finds out that I'm secretly seeing his girlfriend. Oh, my boyfriend knows that I would clean the floor up with him if he ever lies to me about something that serious.

2. To defeat one decisively in a competition. In this usage, "up" is not typically used in the phrase. The final score was 17-1? Wow, we really cleaned the floor with that team!