tilt board

American  

Or tiltboard

noun

1. a rectangular board mounted on a fulcrum, for use by acrobats and gymnasts to gain momentum in feats of tumbling.

2. a similar board, used in exercising, on which the body rests on an inclined plane, with the legs on a higher level than the head and arms.

3. New England.  tilting board.

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Regionalisms

See seesaw.