Misstell
When you accidentally write something and send it to the wrong person in a written communication. Most commonly with Instant Messaging, but also in texting and emailing.
Roo: "Dood Shax's mom is hawt."
Shax: "I's gonna stab you's inda jaw!"
Roo: "Woops misstell!"
Shax: "I's gonna stab you's inda jaw!"
Roo: "Woops misstell!"