A seemingly-ordinary photo which contains nudity, hidden in a surface reflection somewhere.
The exhibitionist strips down, takes a photo containing a shiny object somewhere, and then posts the photo in a public online forum. Some reflectoporn is true fetish -- it gives the exhibitionist the same thrill as flashing strangers in public -- but much of it is done as a joke.
Typically, reflectoporn is posted in the form of an eBay auction item. The listing is for a tea set and includes lots of high-resolution photos. And then after the photos get passed around by giggling bloggers all over the world, the auctioner claims to be "shocked and embarrassed" to learn that -- oh, no! -- the highly-polished silver teakettle <i>actually</i> reflected his willie! And right when he just happened to be fondling himself, too! Talk about awful luck!
Check out this reflectoporn auction...look real closely at the reflection in the car bumper!