Source : Webster's Revised Unabridged Dictionary (1913)

Lancet \Lan"cet\, n. [F. lancette, dim. of lance lance. See
   {Lance}.]
   1. A surgical instrument of various forms, commonly
      sharp-pointed and two-edged, used in venesection, and in
      opening abscesses, etc.

   2. (Metal.) An iron bar used for tapping a melting furnace.
      --Knight.

   {Lancet arch} (Arch.), a pointed arch, of which the width, or
      span, is narrow compared with the height.

   {Lancet architecture}, a name given to a style of
      architecture, in which lancet arches are common; --
      peculiar to England and 13th century.

   {Lancet fish}. (Zo["o]l.)
      (a) A large, voracious, deep-sea fish ({Alepidosaurus
          ferox}), having long, sharp, lancetlike teeth.
      (b) The doctor, or surgeon fish.

Source : WordNet®

lancet fish
     n : large elongate scaleless oceanic fishes with sharp teeth and
         a long sail-like dorsal fin [syn: {lancetfish}, {wolffish}]