What does the idiom above board mean?

Above board means "in a fair, open, or honest manner". It is often used to describe actions that are not hidden or secret. For example, someone might say that a politician is "above board" if they are known for being honest and transparent. The term can also be used to describe things that are not illegal or unethical. For example, a business might say that its practices are "above board" if they comply with all applicable laws and regulations.