Fin·back n. Zool. 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.
n : large flat-headed whalebone whale having deep furrows along
the throat; of Atlantic and Pacific [syn: finback whale,
fin whale, common rorqual, Balaenoptera physalus]