Hambeast is one of those words which may have originated with Something Awful. It refers to people who are porcine, that is, piggishly fat, with arms and legs like hams.
"Look at this picture and tell me Fud isn't a hambeast. How much does he eat in a day?!"
An extremely obese mass of flesh that is collectively thought of as human. To qualify for hambeast, the being must be 100lbs. overweight, but the minimum can travel downwards if the hambeast tries to "show their stuff" when there is glaringly too much of "it."