To wear humble clothes but possess hidden brilliance; to conceal one's true talent or virtue under a modest exterior.
他虽然平时衣着朴素，不爱张扬，实则被褐藏辉，学识渊博，是位真正的学者。
Although he usually dresses modestly and dislikes showing off, he is in fact a person of hidden brilliance with profound knowledge, a true scholar.
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