1. old hat : 老式的, 过时的；
2. send round the hat : 募捐；
3. at the drop of a hat : 立即；
4. under one's hat : 秘密地；
5. talk through one's hat : 胡说八道；
及物动词
名词
参观
1. （常指带檐的）帽子
A hat is a head covering, often with a brim round it, which is usually worn out of doors to give protection from the weather.
2. 角色;职位;工作
If you say that someone is wearing a particular hat, you mean that they are performing a particular role at that time. If you say that they wear several hats, you mean that they have several roles or jobs.
3. 毫不犹豫地;非常乐意地
If you say that you are ready to do something at the drop of a hat, you mean that you are willing to do it immediately, without hesitating.
4. 保守秘密
If you tell someone to keep a piece of information under their hat, you are asking them not to tell anyone else about it.
5. 陈腐;陈旧;老式;过时
If you say that something or someone is old hat, you mean that they have existed or been known for a long time, and they have become uninteresting and boring.
6. 募捐，凑份子（美国英语用 pass the hat）
In British English, if you pass the hat around, you collect money from a group of people, for example in order to give someone a present. In American English, you just say pass the hat .
7. 赞赏;钦佩
If you say that you take your hat off to someone, you mean that you admire them for something that they have done.
8. 向…致敬
If you say 'Hats off to someone', you are expressing admiration for them.
9. （常指没落时）出乎意料地获取（胜利、成功）
To pull something out of the hat means to do something unexpected which helps you to succeed, often when you are failing.
10. （比赛中挑选胜出者时）随机地，任意地
In competitions, if you say that the winners will be drawn or picked out of the hat, you mean that they will be chosen randomly, so everyone has an equal chance of winning.
11. to knock something into a cocked hat - see cocked hat