The Collaborative International Dictionary of English v.0.48:

lancetfish \lan"cet*fish`\, lancet fish \lan"cet fish`\n.
   (Zool.)
   A large, elongated, scaleless, voracious, deep-sea fish
   (Alepidosaurus ferox), having long, sharp, lancetlike teeth
   and a long saillike dorsal fin. [WordNet sense 1]

   Syn: lancet fish, wolffish.
        [1913 Webster + WordNet 1.5]

   2. The doctor, or surgeon fish.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lancetfish
    n 1: large elongate scaleless oceanic fishes with sharp teeth
         and a long dorsal fin that resembles a sail [syn:
         lancetfish, lancet fish, wolffish]