1) The act of assuming an alternate (usually fake) online persona or identity and/or representing yourself as that alternate identity through email, chat, or text messaging communications. Most commonly observed in chat rooms and in singles ads for amusement or gathering attention.
2) Using a keyboard & the internet to pretend to be someone other than what you are, for whatever purpose.
3) Cross-typing is a bit like cross-dressing, with a keyboard instead of clothes (without the gender identity issues).
4) similar to phishing or vishing but done for attention, distraction or photo farming.