Someone who texts a single person so much that it feels like the conversations never end. Sometimes the over-texting is so extreme that the over-textee starts ignoring the over-texter out of annoyance. These types of people are also often the ones who talk a lot.
Candice loves texting with Jeremy but she is a really bad over-texter because of it.
A person who tries too hard to be noticed in WhatsApp groups causing unimaginable harm to good people by writing more than zillion meaningless messages per second
That poor lonely bastard is a major overtexter. I got 10 messages from him in the last five minutes