Wiktionary(0.00 / 0 votes)Rate this definition: mutant(Noun) Something which has mutated, which has one or more new characteristics from a mutation. mutant(Noun) Someone or something that seems strange, abnormal, or bizarre. mutant(Adjective) That has undergone mutation.
Best Answer: The Blue Whale, Balaenoptera musculus, is the largest mammal living today. It is also the largest mammal to have ever lived. In fact the Blue whale is the largest animal ever to have lived on the planet as far as we know; bigger by far than ever the largest Dinosaur.
Blue whales are mammals and not fish. The largest animal that ever lived is the blue whale. The blue whale can weigh 200 tons and measures almost 100 feet. But some other extinct animals were longer, if not heavier than blue whales, most being dinosaurs. Among those of the largest extinct animals are the great sauropod dinosaurs.