A drawing or illustration done by one who is suffering from Insomnia and is bored to death. The pen finds its way into the person's hand and the next thing they know there is a work of art in front of them. Oft times these sketches are tossable garbage, but every now and then one is a real gem.
"Dude, I didn't know you could draw!"
"Me either, it was an insomnisketch."