The name of a really cheaply made medium format camera.
It's made of plastic, with a single shutter speed, three aperature settings, and three focus settings. It was introduced quite a few years ago, so the lenses suck, and rely on the large negative to give acceptable results.
These cameras have severe quality control problems, to the point that no two Dianas have the same shutter speed, and all Dianas have light leaks. Adherents consider these faults to be features.
Though these cameras should have faded to obscurity, artsy photographers have used them to take interesting pictures. People trying to be artsy with cameras followed, and drove the prices of these cameras to around $50 for mint examples. For the same price, one could get other, used medium format cameras that would take much better pictures, at least technically.