The Collaborative International Dictionary of English v.0.48:

Polo \Po"lo\, n. [Of Eastern origin; -- properly, the ball used
   in the game.]
   1. A game of ball of Eastern origin, resembling hockey, with
      the players on horseback.
      [1913 Webster]

   2. A similar game played on the ice, or on a prepared floor,
      by players wearing skates.
      [1913 Webster]

   3. A game similar to hockey played by swimmers.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Polo \Po"lo\, n. [Sp., an air or popular song in Andalucia.]
   A Spanish gypsy dance characterized by energetic movements of
   the body while the feet merely shuffle or glide, with unison
   singing and rhythmic clapping of hands.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Polo
    n 1: Venetian traveler who explored Asia in the 13th century and
         served Kublai Khan (1254-1324) [syn: Polo, Marco Polo]
    2: a game similar to field hockey but played on horseback using
       long-handled mallets and a wooden ball