Any person who attempts to engage in unwanted electronic conversation (ie. texting, instant messaging, etc.) with another person who is concurrently skyping, texting, or messaging another person. (Especially his or her significant other.)
Velma: Hey, so have you talked to Susan lately?
Tracy: I was on facebook chat with her yesterday, but she was on a skype date
with her boyfriend, so she didn't say much.
Velma: God, Tracy, even on the internet, you're still a cyber third-wheel.