Source : Webster's Revised Unabridged Dictionary (1913)

Sea devil \Sea" dev`il\(Zo["o]l.)
   (a) Any very large ray, especially any species of the genus
       {Manta} or {Cepholoptera}, some of which become more than
       twenty feet across and weigh several tons. See also {Ox
       ray}, under {Ox}.
   (b) Any large cephalopod, as a large Octopus, or a giant
       squid ({Architeuthis}). See {Devilfish}.
   (c) The angler.