Defensive Dialing
The act of pulling out your cell phone after seeing someone you know but want to avoid conversing with them. The hope is that they see that you are busy on your phone, so they decide they shouldn't approach you. This must be done before the person notices that you in fact, saw them first.
I saw my old neighbor outside while I was checking the mail today. I pulled out my cell phone and started defensive dialing so that I wouldn't have to get stuck talking to him for the next 10 minutes.