Well, it depends on different contexts, but you can see the sample below and things can be much easier in other contexts.

• One of your friend shared the latest sizzling news, after he finished his exciting talk and wanted you to be crazy about this hot news as well, but, unexpectedly, your reply is that," Hey！ I've already known it. "

(You know what？Your friend assumed that you would be gratful to his revealing, as if  no one else got this news in the world yet~~~hahaO(∩_∩)O~)

Likewise, hypothetics is that your long-term research report that you were proud of it proved to be with a serious mistaken by your little sister. Then, you are really splashed water by your sister.

In a chic word, 囧。

it means

to dampen the enthusiasm of; to put a damper on; to discourage.