A photo, usually a model or celeb, with makeup and photoshopped so bad it looks like a plastic. Like, skin with no pores, someone else's nose, all-new boobs, 20-inch waist, etc. Most published pics are like this. Unhappily, lots of people think that person really exists and wish they looked like them.
That pic of Lady Gaga is so crazy photosucked she looks like a cartoon.