a. [ F. mystèrieux. See 1st Mystery. ] Of or pertaining to mystery; containing a mystery; difficult or impossible to understand; inexplicable; obscure; not revealed or explained; enigmatical; incomprehensible. [ 1913 Webster ]
God at last
To Satan, first in sin, his doom applied,
Thought in mysterious terms. Milton. [ 1913 Webster ]
adv. In a mysterious manner. [ 1913 Webster ]
n.