What is "spring rider"

n. A children's playground item consisting of a large spring beneath a central beam or flange on which the rider sits.

A spring rider or spring rocker is a bouncy, outdoors playing device consisting of a metal spring beneath a plastic or wooden central beam or flange, with 1 to 4 plastic or fiberglass seats above it. When a person sits on it, the structure moves and bounces. Spring riders are common in many playgrounds. They are often designed to look like an animal or a motorbike.