A word中“Word”是“词、字”没错，但是连起来“A word”就不是“一个单词”。

“A word”是“私下里沟通，悄悄话，也可指商谈，谈话”的意思。

举个例子：

Can I have a word with you？

可以借一步说话吗？

I don't think she's interested but I'll have a word with her.

我想她不会感兴趣，但是我会和她聊聊的。

- Tom, can I have a word with you? It won't take long.

- Sure. I'll be with you in a minute.

-汤姆，我能和你说句话吗？不会占用你太多时间。

-好的，我一会儿过来。