adjective
enigmatic
en-ig-MAT-ik/ˌenɪɡˈmætɪk/
Mysterious and difficult to understand.
His enigmatic smile revealed nothing.

Etymology
A riddle conceals meaning beneath obscure words. Enigmatic extends that image to anything mysterious or difficult to understand, as though it were a riddle awaiting interpretation.
In context
I was at first unable to solve these questions but Perpetual attention and time explained to me many appearances which were at first enigmatic
More examples
- The letter contained an enigmatic reference to a missing key.
- She remained an enigmatic figure.
- The inscription was brief and enigmatic.
Forms
enigmatic · more enigmatic · most enigmatic
enigma noun — something puzzling or mysterious
Similar words
- mysterious
- Both are hard to explain; enigmatic suggests a puzzle whose meaning is obscure.
- ambiguous
- Ambiguous allows more than one reading; enigmatic may offer no clear reading at all.