to make someone less able to think clearly or make sensible decisions
cloud somebody's judgement/mind/vision etc
Don't let your personal feelings cloud your judgement.
Fear had clouded his vision.
2 also cloud over [intransitive and transitive]
if someone's face or eyes cloud, or if something clouds them, they start to look angry, sad, or worried:
Ann's eyes clouded with the pain.
Then suspicion clouded his face.
3 [transitive usually passive]
to make something less pleasant or more difficult than it should have been:
Her happiness was clouded by having to leave her son behind.
to make a subject or problem more difficult to understand or deal with, especially by introducing unnecessary ideas:
Uninformed judgements only cloud the issue.
5 also cloud up [intransitive and transitive]
if glass or a liquid clouds, or if something clouds it, it becomes less clear and more difficult to see through:
windows clouded up with steam
The water clouded and I could no longer see the river bed.
to cover something with clouds:
Thick mist clouded the mountaintops.
cloud overphrasal verb
1DN also cloud up American English
if the sky clouds over, it becomes dark and full of black clouds
if someone's face or eyes cloud over, they start to look angry or sad:
His face clouded over in disappointment.