when you are talking to someone who is behind you while walking and they stop, turn a corner, turn around, start talking to someone else, etc. without your knowing. you keep on walking and talking to them even though they aren't there, resulting in stares and strange looks.
I walked down the hallway of my school one monday telling my friend how my weekend was when she turned into the library without my knowing; I was still talking. I was at the end of the hallway when I realized she wasn't there, it was then that I figured out why everyone was giving me funny looks. -Invisible Conversationalism-