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to get cloudy; to cloud over; to become overcast
to cloud up; to fog up; to mist up; to become dim
to be gloomy; to be clouded (expression); to be downcast
to look slightly downward (of a noh mask; indicating sadness, grief, etc.)
午後から急に空が暗く曇ってきたね。
The sky suddenly got dark and cloudy in the afternoon.
メガネが曇ってしまった。
My glasses fogged up.
眼鏡が曇って前が見えない。
My glasses fogged up and I can't see ahead.