Entry from OED Online

bouncy castle (orig. and chiefly Brit.), a large inflatable, typically in the form of a stylized castle or other building, on which people (esp. children) can jump and play.
 
  1986 Guardian 9 Dec. 14/2 Supervised children's holiday activities..; fun sessions including rollerskating, swimming, and *bouncy castle. 1992 Which? Aug. 416/3 Before you let your children loose on an inflatable bouncy castle, make sure that..there are soft gym mats covering hard surfaces near open sides or fronts. 1997 Daily Tel. 24 Mar. 10/4 The bouncy castle takes seven hours to inflate, can accommodate 200 bouncers at a time and is made from white plastic.