不明觉厉

bù míng jué lì

I do not understand it, but it sounds impressive

Character by character

不bù
not

明míng
understand

觉jué
feel

厉lì
formidable

他讲的那些专业名词，我听了只有不明觉厉。

All those technical terms he used: I could only be impressed without understanding.

Tone: neutral.

An internet coinage from about 2013, built like a chengyu.

Learn this in Lesson 212 · HSK 9+: 网络流行语 (Internet slang)

A dialogue, a reading, word cards with audio and a drill that uses it, in Learn Chinese with Bao. The first lessons of every level are free.