To become cloudy or overcast (referring to the sky or weather).
午後から空が曇ってきたので傘を持って行ったほうがいい。
The sky clouded over in the afternoon, so you should take an umbrella.
今日は曇っていて富士山が見えない。
It's cloudy today and Mount Fuji can't be seen.
天気予報によると、明日は一日中曇るらしい。
According to the weather forecast, it will be overcast all day tomorrow.
To fog up or become misted (e.g., glasses, windows); to become dim or hazy.
寒い日にマスクをすると眼鏡が曇る。
On cold days, wearing a mask causes glasses to fog up.
風呂場の鏡が曇って文字が見えない。
The bathroom mirror is fogged up and I can't see the writing.
レンズが曇って写真がぼやけた。
The lens fogged up and the photo came out blurry.
To be gloomy or to have a clouded expression; to look downcast or troubled.
彼の顔が曇ったのを見て、何かあったと感じた。
Seeing his face cloud over, I felt something had happened.
いい雰囲気だったが、その一言で場が曇った。
The mood had been pleasant, but that one remark put a damper on things.
彼女は急に表情が曇り、話をやめた。
Her expression suddenly clouded over and she stopped talking.
In Noh theater, the mask's slight downward tilt that conveys sadness or grief (specialized usage).
能の演技では面が曇ることで複雑な感情を表すことがある。
In Noh performance, the mask's subtle tilt can express complex emotions.