The Collaborative International Dictionary of English v.0.48:

Polonaise \Po`lo*naise"\, a. [F. polonais, polonaise, Polish.]
   Of or pertaining to the Poles, or to Poland. [Written also
   Polonese.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Polonaise \Po`lo*naise"\, n. [Written also Polonese and
   Polonoise.]
   1. The Polish language.
      [1913 Webster]

   2. An article of dress for women, consisting of a body and an
      outer skirt in one piece.
      [1913 Webster]

   3. (Mus.) A stately Polish dance tune, in 3-4 measure,
      beginning always on the beat with a quaver followed by a
      crotchet, and closing on the beat after a strong accent on
      the second beat; also, a dance adapted to such music; a
      polacca.
      [1913 Webster]

WordNet (r) 3.0 (2006):

polonaise
    n 1: a woman's dress with a tight bodice and an overskirt drawn
         back to reveal a colorful underskirt