finback(n = noun.animal) balaenoptera physalus, common rorqual, fin whale, finback whale - large flat-headed whalebone whale having deep furrows along the throat; of Atlantic and Pacific;
is a kind of razorback, rorqual
is a member of balaenoptera, genus balaenoptera

   Any whale of the genera Sibbaldius, Balænoptera, and allied genera, of the family Balænopteridæ, characterized by a prominent fin on the back. The common finbacks of the New England coast are Sibbaldius tectirostris and S. tuberosus. [1913 Webster]

finback whale