The term 'beyond reproach' is used to describe someone or something that is beyond criticism or fault. This can be seen in the four crossword solutions given: IMPECCABLE (10 letters), HONEST (6 letters), squeakyclean (12 letters), and unexceptionable (15 letters). IMPECCABLE means flawless, HONEST implies truthfulness, squeakyclean suggests purity, and unexceptionable means without fault. Together, these words suggest that someone or something is beyond reproach, meaning they are perfect and without any flaws.