An ambulocetus is an incredibly fat person. This person is beyond whale fat. the term comes from the /fit/ board on 4chan. an ambulocetus was a large land mammal that evolved into whales. it has been called the walking whale, so fatasses are now called ambulocetus's on /fit/
Yeah dude, she's totally an ambulocetus
Literally "walking whale", it's a mean-spirited way of describing an obese person. Essentially, it's a stealthy or mocking pseudo-technical way of saying "landwhale".
Did you see that ambulocetus who waddled into the store the other day? She must have weighed 400 lb!