When chatting online with friends, it's actually quite common to see "汗 (hàn)," so much so in fact, that it's become a widely used expressi0n in our daily non-Internet based lives as well.
When you witness someone do something unusual, or extraordinary, you can express your astonishment by uttering "汗(hàn)." This usage of the word actually originated from a cartoon.
Finally, "汗 (hàn)" is a verb used to show emotions of embarrassment or shame.
Let's review the three common meanings of "汗 (hàn)."
First, to express a sense of surprise or shock when something exceeds expectations. It's English equivalent is along the lines of "wow," "holy cow," or "oh my!"
Example:
Hàn, nǐ jìngrán chī wán le zhème dà yí ge hànbǎo!
汗, 你 竟然 吃 完 了 这么 大 一个 汉堡!
Wow…you actually managed to finish that huge hamburger!
Second, to express a sense of embarrassment.
Example:
Hàn a, wǒ jìngrán bǎ yīfu chuān fǎn le.
汗 啊,我 竟然 把 衣服 穿 反 了。
How embarrassing, I had my clothes on backwards.
Last, to express being at a loss for words, or not having any reaction.
Example:
Hàn, wǒ zhēn bu zhīdao shuō shénme hǎo le.
汗, 我 真 不 知道 说 什么 好 了。
Oh…I really don't know what to say.