Abbreviation for the initialism "Laughing With My Dick Out". This response would be appropriate if instant messaged something humorous while masturbating to porn, or for just general internet responding while nude.
Jones while browsing porn = fap fap fap
AIM Sound: BBBBBRRRRINNNNNGGGGGG
Craig: Did you hear about the guy with the five penises?
Jones: no.. I'm kind of in the middle of something.
Craig: His pants fit like a glove.