(Zool.), a rather large and swift baleen whale of the northern Pacific (Eschrichtius robustus, formerly Rhachianectes glaucus), having short jaws and no dorsal fin; -- called also grayback, devilfish, and hardhead. It grows to a length of 50 feet (sometimes 60 feet). It was formerly taken in large numbers in the bays of California, and is now rare. It lives up to 50 or 60 years and adults weigh from 20 to 40 tons. [ 1913 Webster + PJC ]