mí​tuán HSK7

enigma

谜团 (謎團) mí​tuán
enigma noun
a mystery or riddle that is difficult to understand or explain

The truth behind that disappearance case remains a deep mystery.

unpredictable situation noun
an elusive or complex set of circumstances that is difficult to foresee or grasp

Frequency

Movie subtitles
3.13 per million appears in 1% of films
Written text
1.60 per million

Details

HSK 3.0
Level 7

Sources

Definitions
CC-CEDICT