Noun
A device used for recreation, athletic training, circus acts, etc. consisting of a rectangular or circular board on a fulcrum on which board the user attempts to balance.
Hyponyms: rocker board, rocker-roller board, wobble board, sphere-and-ring board
(video games) A device that measures the centre of balance of a player standing on it, used to provide motion input to sport-themed games etc.
Source: en.wiktionary.org