Aboveboard is a term that describes something that is honest, straightforward and open. Some synonyms that could be used in place of aboveboard include forthright, candid, transparent, frank, and open. "Forthright" refers to being direct and honest, without any hesitation or evasion. "Candid" means being completely honest and straightforward, often in a situation where the stakes are high. "Transparent" is used to describe something that is easily understood and doesn't hide anything. "Frank" refers to speaking one's mind openly and honestly. "Open" means being willing to communicate and share information without any hidden motives or agendas. All of these synonyms convey the same sense of being honest and trustworthy, just like aboveboard.