Added to the end of a text message when you don't want the other person to respond.
Usually used when one only has a certain number of text messages per month, and doesn't want to waste one by having somebody give an obvious response to the initial text.
Guy1 to Guy 2: dtb?
Guy2: sure, gimme a min.
Guy2 to Guy3: hey man me and a few others are dtb, u in?
Guy3: Fuck yeah, lez bang!