The act of falling asleep with your hand on the mouse while
surfing the web, and randomly clicking and moving it in your sleep, often ending up with
something on the screen you were not looking at when you fell asleep.
To other people present, it's like seeing a puppy moving it's legs during a nap, but to the
unfortunate sleeper there will be a little concern when he/she will wake up and see something unexpected on the screen, just like sleepwalkers waking up not in their beedroom.
See also RMM (Rapid Mouse Movements).