When one person walks past another, encroaches the other one's personal space and fails to acknowledge the error.
1st co-worker: "While I was getting on the bus this morning, a guy jumped off through the front door, nearly knocking me over. He didn't bother to say either "Excuse me" or "Good morning". We were close enough to kiss, but I was turned off by his clogged pores."
2nd co-worker: "Oh, that's ugly rude