Mysterious

Part of speech: adjective (a.)

Of or pertaining to mystery; containing a mystery; difficult or impossible to understand; obscure not revealed or explained; enigmatical; incomprehensible. God at last To Satan, first in sin, his doom applied, Thought in mysterious terms. Milton.

Synonyms: Obscure; secret; occult; dark; mystic; cabalistic; enigmatical; unintelligible; incomprehensible.