lurkerbater

A person who anonymously watches a chat room while strumming their filthies.

There are 2 of us chatting but I see a third person is reading. It must be Raven, the original lurkerbater.

lurkerbater by Kaiservonschizen March 19, 2014

Lurkerbating 

To masturbate to something someone else is doing inconspicuously.

"I caught Dylan lurkerbating outside my window while I was looking up porn!"
Cody-You should close your blinds when you do that.

Lurkerbating by The Guy With The Pants January 25, 2011