[1] : The Collaborative International Dictionary of English v.0.48

waistcoat \waist"coat\, n.
      a a short, sleeveless coat or garment for men, worn
          under the coat, extending no lower than the hips, and
          covering the waist; a vest.
      b a garment occasionally worn by women as a part of
          fashionable costume.
          1913 webster

   note: the waistcoat was a part of female attire as well as
         male . . . it was only when the waistcoat was worn
         without a gown or upper dress that it was considered
         the mark of a mad or profligate woman. --nares.
         1913 webster

   syn: see vest.
        1913 webster
see also:
vest 

[2] : WordNet (r) 2.0

waistcoat
     n : a man's sleeveless garment worn underneath a coat syn: vest
see also:
vest 

Waistcoat >> W Words
Waistcoat, definition of term: Waistcoat
waistcoat_pag1.html