Source : Webster's Revised Unabridged Dictionary (1913)

Sea louse \Sea" louse`\ (Zo["o]l.)
   Any one of numerous species of isopod crustaceans of
   {Cymothoa}, {Livoneca}, and allied genera, mostly parasites
   on fishes.

Source : WordNet®

sea louse
     n : marine isopod crustacean [syn: {sea slater}]