在开会是“at a meeting”还是“in a meeting”?最好有确定，又根据的出处

在开会是“at a meeting”还是“in a meeting”?最好有确定，又根据的出处

回答：
at a meeting和in a meeting都可以说，请看实例(大都出自权威词书)：
Officially, the director is in a meeting, though actually he’s playing golf. 据说主任正在开会，可他实际上正打高尔夫球呢。——见《牛津高阶英汉双解词典》(第四版) (officially词条)
I’m tied up in a meeting until 3 pm. 我开会直到下午三点钟方可脱身。——见《牛津高阶英汉双解词典》(第四版) (tie词条)
Sorry to keep you waiting—I got stuck in a meeting. ——见《朗文当代英语词典》(1995年版) (keep词条)
Mrs Lavelle is in a meeting at the moment. ——见《朗文当代英语词典》(1995年版) (meeting词条)
There were three others present at the meeting besides us. 除了我们之外，还有其他三人个出席了会议。——见《朗文多功能分类词典》(besides词条)
He took the chair at a meeting some time ago. 前些日子他主持了一次会议。——见王福祯编著《新时代英语惯用法词典》第195页。
There were both blacks and whites at the meeting. 参加会议的有黑人也有白人。——见周贞雄编著《大学英语重点词用法手册》besides词条)
She might be invited to speak at the meeting. 她可能被邀在会上发言。——见张道真编著《张道真英语语法》第116页。

attending a meeting
taking part in a meeting

at the meeting 指的是在会议中 在会议上 in the meeting 指的是 在开会

at a meeting:
在开会

Examples:
1. I'm sorry I'm late; I was at a meeting and couldn't get away.
对不起，我来晚了。刚才我在开会，不能脱身。
2. Mr Hood said that he would have to go on, as he was due at a meeting at eleven o'clock.
胡德先生说由于他11点钟要出席一个会议，得先走一步了。
3. He generally keeps silent at a meeting.
他通常在会上保持沉默。
4. "Don't say yes at a meeting and go back on your words and say no after it."
"不要开会时赞成，会后又反悔说不赞成。"