1. C U 云　 visible water vapour floating in the sky
2. C 团，群　 mass of smoke, dust, sand, etc. in the air; mass of insects moving together in the sky
3. C 造成不愉快或不明朗的事物　 thing that causes unhappiness, uncertainty, etc.

　blow ～s　吞云吐雾
　disperse ～s　吹散乌云
　pierce the ～s　耸入云霄
　dark ～　乌云
　dense ～　浓云
　fleecy ～　白云
　fleeting ～　疾驰的云朵
　fluffy white ～　绒毛状的白色云朵
　mushroom ～　蘑菇云
　radioactive ～　放射云
　storm ～　暴风云
　war ～　战争乌云
　above ～　在云上
　in ～　成群
　under the ～　在云层的笼罩下
　up into the ～　升入云层

　Not a single cloud is to be seen.　一朵云也看不见。
　Gleams of sunshine came through the breaks of the cloud.　太阳的光束从云隙中透射出来。
　The top of the mountain was covered in cloud.　浮云遮盖着山顶。
　I wandered like a lonely cloud.　我像一朵孤云遨游。
　The sky came over dark as a thick cloud passed before the sun.　乌云蔽日，天色一时昏暗起来。
　Every cloud has a silver lining.　乌云背后总有一线光芒。
　The clouds are gathering for a storm.　阴云密布，看来快下暴雨了。
　The clouds soon cleared away and it became quite warm.　云很快散去，天气变得非常暖和。
　White clouds floated in the sky.　天空中飘着朵朵白云。
　There are so many clouds today.　今天云特别多。
　Ugly clouds gathered on the horizon.　险恶的云层在地平线上密集。
　Masses of dark clouds melted away.　大块大块的乌云消散了。
　The heavy clouds have made this a gloomy day.　密云使今天很昏暗。
　The skyscraper pierces the clouds.　摩天大楼高耸入云。
　Look at those clouds. They are purple.　看那些云，是紫色的。
　The sky is covered with dark clouds.　天空乌云密布。
　It is ragged clouds driven by the wind.　那是被风吹散的残云。
　That evening was dark with clouds.　那天黄昏由于多云而很阴暗。
　These high summits are seldom free from clouds.　这些高山顶上难得没有云在那里。
　The mosquitoes were coming in clouds.　蚊虫一大群一大群地飞来。
　He made his way to the exit in a cloud of security men.　他在一大群保卫人员的前呼后拥下走向出口。
　The darkest cloud has been lifted from the future.　涉及将来最暗淡的疑云一扫而光了。
　When they married, there were no clouds on their happiness.　他们结婚时并不存在影响他们幸福的因素。
　A cloud of suspicion is hanging over him.　有一团疑云笼罩着他。

 ♣ cast a cloud on〔over〕
　在…上投下一层阴影　make sth not very happy
　I am sorry to cast a cloud on the party, but I am afraid there's been some bad news.　很抱歉给聚会抹上了一层阴影，可是恐怕有些坏消息要告诉大家。
　His miserable manner cast a cloud over the whole proceedings.　他痛苦的样子给整个活动投下了阴影。
　His arrival cast a cloud over the meeting.　他的到场给这次会议投下了阴云。
 ♣ in the clouds
1. 在高空中 in the sky
　We can see a plane flying in the clouds.　我们能看到在高空中飞的飞机。
2. 想入非非，爱幻想 just like to consider, but dislike to do
　All the way home I was in the clouds.　在回家的路上我一直都在想入非非。
　He is always in the clouds.　他总爱幻想。
　A good artist should have his head in the clouds sometimes, but his feet always on the ground.　一位好的艺术家有时应富于幻想，但始终要脚踏实地。
 ♣ on cloud nine
　极快乐　extremely happy
　He was on cloud nine after winning the competition.　他在比赛胜利后欣喜若狂。
　She has been on cloud nine since the magazine printed the story she wrote.　自从那份杂志发表了一篇她写的故事后，她高兴得不得了。
 ♣ under a cloud
　受到怀疑　being doubted
　She was always under a cloud at the office.　她在办公室里经常受到怀疑。
　Joyce has been under a cloud since her roommate's bracelet disappeared.　自从室友的手镯不见以后，乔伊斯一直受到怀疑。
　The butcher is under a cloud because the inspectors found that his scales were not honest.　这个卖肉商丧失了信誉，因为检查人员发现他的秤缺斤短两。
　Your reputation was under a cloud.　你的名誉受到了怀疑。
 ♣ under cloud of night
　趁黑夜　when it is dark
　They broke into our house under cloud of night.　他们趁黑闯进了我们的房子。
　He tried to escape under cloud of night.　他想趁黑逃跑。

　你能看见那架在高空中飞行的飞机吗　?
　［误］ Can you see the plane flying in clouds?
　［正］ Can you see the plane flying in the clouds?
　［析］ in the clouds可表示“在高空中飞”， the不可以省略。

1. vt. & vi.（使）某物变得阴沉暗淡，不清楚　 (cause sth to) become dull, unclear or indistinct
2. vt. & vi.（使）某人的脸显得阴沉或忧伤　 (of sb's face) show sadness or worry

　～ beer　使啤酒变浑浊
　～ friendship　影响友谊
　～ issue　把问题搞得模糊不清
　～ memory　记忆模糊
　～ mind　使思绪不清
　～ mirror　使镜子模糊不清
　～ mountain　遮住山
　～ sky　天空布满乌云
　～ over　布满乌云，脸色变得阴沉
　～ up　（使）模糊，变得模糊
　～ with　因…而模糊

　Her eyes clouded with tears.　她泪眼模糊。
　Her brows clouded with worry.　她显出忧虑的神色。
　His face clouded at the mention of Grandpa's name.　一提起祖父的名字，他脸色就阴沉起来。
　That's a separate argument and it will only cloud the issue.　这是另外一项争论，它只会把问题搞乱。
　Her breath clouded the mirror.　她呼出的气使镜子变得模糊不清。
　The thick mist clouded the mountains.　浓雾遮住了群山。
　All these troubles have clouded his mind.　所有这些烦恼已使他思绪不清。
　You'll cloud the beer if you shake the barrel.　如果你摇晃酒桶，啤酒就会变浑浊。
　I hope this disagreement won't cloud our friendship.　我希望这一分歧不会影响我们的友谊。
　The sky is darkly clouded.　天空乌云密布。
　His judgment was clouded by selfishness.　自私毁了他的判断力。

 ♣ cloud over　(v.+adv.)
1. 布满乌云 be covered with dark cloud
　The sky clouded over before the storm.　暴风雨来临前，天空阴云密布。
　Just as we were beginning to enjoy the sunshine, the sky clouded over and a cold wind began to blow.　正当我们准备欣赏一下阳光时，天空突然乌云密布，刮起了冷风。
2. 脸色变得阴沉 cause sb's face to show sadness
　When he heard the news of his friend's accident, his face clouded over.　他听到朋友发生事故后，脸色变得阴沉下来。
　Mary's face clouded over when she heard the bad news about her mother's operation.　当玛丽听到有关她母亲动手术的坏消息时，她的脸色变得阴郁起来。
 ♣ cloud up　(v.+adv.)
　（使）模糊，变得模糊　cause sth not clear
　My glasses have clouded up after I entered the room.　我进屋后眼镜变得模糊了。
　The windows have clouded up in the steam.　窗户在水汽中变得模糊不清了。
　The steam has clouded the windows up.　蒸汽使窗户变得模糊不清。

　［词源］　古英语clud（岩石，小山）