My co-worker (Jeff) and I were discussing the disparity between people who say “LOL” in IM but are, in fact, not laughing out loud. He suggested that it was really laughing internally loudly, so I suggested LiL. I then told him that when I do so, I am laughing uproariously in the machine world.
Jeff then coined this term: LUITMW. Go forth and copy Interwebs!