black whale
      n 1: small dark-colored whale of the Atlantic coast of the United
           States; the largest male acts as pilot or leader for the
           school [syn: pilot whale, common blackfish, blackfish,
            Globicephala melaena]
      2: large whale with a large cavity in the head containing
         spermaceti and oil; also a source of ambergris [syn: {sperm
         whale, cachalot, Physeter catodon]