From ibikeu Wiki
Bike polo, similar to equestrian polo, is a team sport played on bicycles in which the object is to score goals against an opposing team. There are many local variations on bike polo, including playing on grass or street ("hardcourt"), the type of balls and mallets used, and the particular rules. There are national leagues in the United States, India and perhaps elsewhere, which play a more proper game like the equestrian version. There are also many local
DIY groups in the US and other cities that play a game that can be faster, rougher, and perhaps funner.
For more information on bike polo in general visit Wikipedia's Bike Polo article.