The symbol located in any chat showing that the other person is typing. This usually happens after a pause in conversation or a wrong turn in the chat. Usually a person begins to type to keep the conversation going but sees the other person typing too and out of laziness lets the other say something pointless.
Guy 1. It's so hard to keep a convo with this girl.
Guy 2. Why's that?
Guy 1. She's so random, if I didn't see her Writing Sign this conversation wouldn't make any sense!