The phrase "was above-board" refers to something that was honest, open, and transparent. Antonyms for this phrase include words such as deceptive, dishonest, fraudulent, and underhanded. These words imply that something was done in a secretive or misleading way, often with the intention of covering up the truth or gaining an unfair advantage. When something is not above-board, it may be difficult to trust or rely on, and it can damage relationships, reputations, and businesses. Therefore, it is important to always strive for honesty and openness, and to avoid behaviors or actions that could be seen as below-board or unethical.