We were unable to define what exactly was wrong with him...

我们说不清楚他到底哪里不对劲。

He was asked to define his concept of cool.

他被要求说明自己关于“酷”的定义。

When people are asked 'What is intelligence?' they tend to reply: 'I don't know how to define it, but I can certainly recognize it when I see it.'...

当被问及“智力是什么”的时候，人们往往会回答说：“我不知道该如何定义它，但我见到了肯定就能认得出。”

Collins English Dictionary defines a workaholic as 'a person obsessively addicted to work'.

《柯林斯英语词典》给“工作狂”一词下的定义是“一个过分沉溺于工作中的人”。