rebounder
n.— «The room also has a rebounder, a small trampoline used for stimulating the lymphatic system.» —“Create sacred spaces in home” by Mary Beth Breckenridge Akron Beacon Journal (Ohio) Jan. 30, 2009. (source: Double-Tongued Dictionary)
trampoline effect n.— «Wood bat advocates are concerned that balls hit off metal bats are subject to what is known as a trampoline effect: When a ball hits a wooden bat, the ball compresses at the instant of impact and loses much of its energy...