The Collaborative International Dictionary of English v.0.48:

Tailing \Tail"ing\, n.
   1. (Arch.) The part of a projecting stone or brick inserted
      in a wall. --Gwilt.
      [1913 Webster]

   2. (Surg.) Same as Tail, n., 8
      (a) .
          [1913 Webster]

   3. Sexual intercourse. [Obs.] --Chaucer.
      [1913 Webster]

   4. pl. The lighter parts of grain separated from the seed
      threshing and winnowing; chaff.
      [1913 Webster]

   5. pl. (Mining) The refuse part of stamped ore, thrown behind
      the tail of the buddle or washing apparatus. It is dressed
      over again to secure whatever metal may exist in it.
      Called also tails. --Pryce.
      [1913 Webster]

   6. (Elec.) A prolongation of current in a telegraph line, due
      to capacity in the line and causing signals to run
      together.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

tails
    n 1: formalwear consisting of full evening dress for men [syn:
         dress suit, full dress, tailcoat, tail coat,
         tails, white tie, white tie and tails]