"Yīn tiān" literally combines 阴 (yīn), meaning 'overcast', 'shady', or 'cloud-covered', and 天 (tiān), meaning 'sky' or 'day'. Together, they form a noun meaning 'overcast day'—a day when thick cloud cover blocks most or all sunlight, resulting in dim, gray light and no direct sun. It is a neutral, descriptive weather term used in daily conversation, forecasts, and writing.

This word describes a specific atmospheric condition—not rain, fog, or wind, but persistent cloudiness that suppresses brightness and warmth. Unlike "xù yǔ" (drizzling) or "bào yǔ" (downpour), "yīn tiān" implies dry, cloudy weather; precipitation may or may not follow. It’s commonly used to explain mood, clothing choices, or outdoor plans—for example, people might say it’s too gloomy for hiking or ideal for photography due to soft lighting.