Mys*te"ri*ous (?), a. [F. mysterieux. See 1st Mystery.]
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.
Syn. -- Obscure; secret; occult; dark; mystic; cabalistic; enigmatical; unintelligible; incomprehensible.
© Webster 1913.