rorqual(n = noun.animal)razorback - any of several baleen whales of the family Balaenopteridae having longitudinal grooves on the throat and a small pointed dorsal fin;
A very large North Atlantic whalebone whale (Physalus antiquorum, or Balænoptera physalus). It has a dorsal fin, and strong longitudinal folds on the throat and belly. Called also razorback. [1913 Webster]