Source : Webster's Revised Unabridged Dictionary (1913)

Petticoat \Pet"ti*coat\, n. (Zo["o]l.) [Petty + coat.]
   A loose under-garment worn by women, and covering the body
   below the waist.

   {Petticoat government}, government by women, whether in
      politics or domestic affairs. [Colloq.]

   {Petticoat pipe} (Locomotives), a short, flaring pipe
      surrounding the blast nozzle in the smoke box, to equalize
      the draft.

Source : WordNet®

petticoat
     n : undergarment worn under a skirt [syn: {half-slip}, {underskirt}]