1. a white or grey mass of very small drops of water in the sky
2. a large amount of smoke, dust, steam etc in the air
3. something unpleasant that spoils an activity, event, or situation
4. a feeling of being depressed or unhappy (‘have a cloud hanging over you’)
Origin and usage
The word cloud comes from the Old English word ‘clud’ meaning ‘rock mass, hill’. The word emerged sometime in the 1300s to describe the visible masses of evaporated water seen in the sky because these masses looked a lot like rock formations. Figurative uses of the word cloud came later, including to describe feeling sad or depressed in 1500.
The word cloud is most often used in the study of weather science to describe the large masses of evaporated water seen in the sky. Clouds can appear white or grey, and there are four main types of clouds: cirrus, cumulus, stratus and nimbus.
The four cloud classifications were named by an amateur British weather scientist – or meteorologist – named Luke Howard in 1802. Howard believed studying clouds could give clues about the weather.
Cirrus clouds tend to look thin and wispy, like long streamers or ribbons. They are white and predict fair, pleasant weather.
Cumulus clouds are large and puffy and look like balls of cotton wool. These clouds are also usually white and indicate good weather.
Stratus clouds look like large grey blankets hanging low in the sky. Fog is a kind of stratus cloud.
Nimbus clouds are dark grey and low-hanging in the sky. They always produce precipitation – that is, water that falls from the sky in the form of rain or snow.
View the full definition in the Macmillan Dictionary.
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