The adjective ambiguous means that something is unclear or confusing as it can be understood in more than one way.  

Synonyms are obscure, uncertain, dubious or cryptic.

The word origins from Latin ambiguus (1520s) “having double meaning, shifting, changeable, doubtful” and from the adjective ambigere (ambi = about, and agere = drive, lead, act). A declining use of the word in the 19th century, but then in the 20th century when the “archaic” word really made a comeback and picked up again in use.

Her eyes are of an ambiguous color.

We noticed it was a joke from his ambiguous smile.

The teacher made the imagery ambiguous, to allow space for individual interpretation.