noun

1. A curved piece of wood attached to the bottom of a rocking chair or cradle that enables it to rock back and forth.

2. A rocking chair.

3. The lengthwise curvature of a surfboard. (More rocker is a more curved board.)

   “All modern surfboards share a similar rocker design — Bruce Jones https//web.archive.org/web/20051212041317/http://www.brucejones.com/longboar.htm”