Looks like a big ole Tom feral cat - shot one out of a squirle nest once - that thing was huge. They'll get bigger than the average cat after living wild for awhile.

Don't know if this is true or not but I was once told that a cat can continue to grow its entire life depending on environment and food conditions - don't quote me one this though I heard that somewhere once and never really followed up with any reseach on it of my own.