HHP is a popular online abbreviation for “haha point”. "Haha" is an echoic word for laughter in Chinese and "point" is the Chinese equivalent of "threshold." Therefore, haha point refers to the threshold where you can be amused and burst into laughter.

HHP是網絡上流傳的“笑點(haha point)”這個詞英文說法的縮寫形式。Haha(哈哈)是漢語中形容笑聲的象聲詞，point(點)在漢語中指“門檻”或“基準線”。那么，“哈哈點”(即“笑點”)指的就是能夠讓你發笑的那個點。

If we say someone has a quite low haha point, that means he can be very easily amused.

如果我們說某人的笑點很低，那就是說這個人很容易被逗樂。

在醫學中，“痛點”就是用pain point來表示的，估計這個haha point也是從這里衍生而來的吧。