Overshadowing the sky and obscuring the sun. Used to describe something extremely vast in size, numerous in quantity, or possessing an overwhelming momentum/presence.
茂密的森林遮天蔽日，阳光很难穿透，形成了一片凉爽的绿荫
The dense forest overshadowed the sky and obscured the sun, making it difficult for sunlight to penetrate and forming a cool green canopy.
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