Real Dictionary

polo
uncountable noun: Polo is a game played between two teams of players. The players ride horses and use wooden hammers with long handles to hit a ball.

Polo in American English
ˈMarco (ˈmɑrkoʊ ) 1254-1324; Venetian traveler in E Asia
a game played on horseback by two teams of four players each, who attempt to drive a small wooden ball through the opponents' goal with a mallet having a long, flexible handle
noun: a game played on horseback between two teams, each of four players, the object being to score points by driving a wooden ball into the opponents' goal using a long-handled mallet

polo in British English
noun: a game similar to hockey played on horseback using long-handled mallets (polo sticks) and a wooden ball
noun: Marco (ˈmɑːkəʊ ). 1254–1324, Venetian merchant, famous for his account of his travels in Asia. After travelling overland to China (1271–75), he spent 17 years serving Kublai Khan before returning to Venice by sea (1292–95)