when you talk to someone three different ways at the same time, keeping up the conversation. eg. on facebook, sms, msn, calling them, talking to their face.
steph (facebook) : omgg ssaraah!
sarah (sms) :what!?!
steph (textplus) : we are triangle texting!!!!!
sarah (sms) : aww yeah!
(5 minutes later)
steph (facebook) : wait, what did you say? lets stay on one program, im so confused!