adv.1.Under the board, or table; hence, secretly; unfairly; underhand. See the Note under Aboveboard.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
We also replaced the underboard lights with stylish low-voltage bulbs.
He was placed on a wooden underboard inside a wicker coffin and carried on the shoulders of family members towards the building.