Source : Webster's Revised Unabridged Dictionary (1913)

Rat-tail \Rat"-tail`\, a.
   Like a rat's tale in form; as, a rat-tail file, which is
   round, slender, and tapering. See Illust. of {File}.

Rat-tail \Rat"-tail`\, n.
   1. (Far.) pl. An excrescence growing from the pastern to the
      middle of the shank of a horse.

   2. (Zo["o]l.)
      (a) The California chim[ae]ra. See {Chim[ae]ra}.
      (b) Any fish of the genus {Macrurus}. See {Grenadier}, 2.