rumpus room 
noun North American & Australian /NZ
A room for playing games, typically in the basement of a house.The former is an efficient enclosure clad in recycled hardwood, with bedrooms above a rumpus room, services and garage....
- There is a rumpus room and the living area is very spacious and has air-conditioning for your comfort.
- Other ground floor accommodation consists of a bathroom, three bedrooms, two of which will become a library/computer room and a rumpus room when upstairs is complete.