When a phone company is not able to transfer old phone numbers to a newcell phone and you deliberately do not enter certain numbers in the new cell phone.
A - Hey, what's going on?
B - Who is this?
A - This is Mike.
B - Oh sorry. I dephoned you when I got my newcell phone.
An adjective given when someone has mistakenly made themselves lookdumb by saying something abnormally stupid in a conversation. Someone who disrupted, or killed, the conversation with a bad joke or comment.
"Dude! Guess what!"
"Chicken butt!"
"...You are really dephonicated, do you know that?"