Bughouse Chess

Bughouse chess = game on 2 chessboards, between which taken material is travelling ...
This modern realtime chess variant involves two boards placed side by side, two sets, four players, and two clocks. 
The players sitting side by side are partners and play opposite colors. 
When you capture a piece, you give it to your partner. 
When it's your turn, you can either move one of your onboard pieces, or drop one of your offboard pieces on an empty square. 
Your team loses if you get checkmated or run out of time. 

See http://bughousechess.wz.cz/CompleteBughouseChessRules.htm
