如果有人对你说“Out to lunch”，你第一反应是不是 “出去吃午饭”？其实，“Out to lunch”正确的意思是：心不在焉，魂不守舍；疯狂的；神志不清的；过时的；懒散的，稀里糊涂的，神经病的。
所以，有老外和你说out to lunch要小心了，可能是说你是不是“稀里糊涂的”。
例句：
It seems that you were out to lunch in.
你上课时似乎心不在焉。
Don't listen to him, he's out to lunch.
别听他的，他心不在焉。
This guy is really out to lunch.
这家伙真的心不在焉。
She's gone completely out to lunch.
她完全疯了。
What are you saying? You are out to lunch.
你在说什么？你看起来有点神志不清啊。
You'll always find us out to lunch!
你应该能够发现，我们总是心不在焉！
You must have been out to lunch when you wrote that weird report.
当你做这个奇怪的报告的时候，你一定是神志不清的。
但是，如果你想表达“带某人出去吃（午）饭”，可以说take sb (out) to lunch。
Reichel took me out to lunch.
雷赫尔请我出去吃的午饭。《柯林斯高阶英汉双解学习词典》
I'll take you out to lunch when I get back.
我回来后带你出去吃午饭。
也就是要根据语境加以理解，不要想当然。其实“出去吃午饭”
也可以这么说就不容易产生误解：go out for lunch.
Let's go out for lunch ─ my treat.
咱们到外面去吃午餐，我请客。《牛津高阶英汉双解词典》
Why don't we close up and go out for lunch?
我们为什么不关上门出去吃顿午饭？
I'll probably go out for lunch with my colleagues at twelve.
我大概会在12点和同事一起出去吃午饭。
