The first two characters, 光明 (guāngmíng), literally mean “bright light,” creating a metaphor for total visibility and lack of darkness or secrecy. The last two, 正大 (zhèngdà), mean “upright and grand,” implying a moral correctness and noble scale. Together, 光明正大 paints a vivid picture of someone acting with great moral integrity under a bright, revealing light, completely open and righteous.