The act of desperately reaching out to an ex who has shown no interest in continuing communication. The process of trying to find the magic combination of words that will elicit a response from someone who is obviously not interested in talking to you.
The original Timmy Text was sent by a girl to an ex who had not responded to multiple emails and texts over the last several weeks. In a fit of desperation and patheticness she sent him a text that said "I miss you and so does Timmy". Timmy being a stuffed teddy bear he had given her. So pathetic was this action that all behavior similar to it is referred to as "being Timmy".
Girl: I just got a text from Chris that said "just checking in, haven't heard from you in awhile."
Friend: omg. that is SUCH Timmy Text. He needs to get a clue.