a puzzling or inexplicable occurrence or situation:
His disappearance is an enigma that has given rise to much speculation.
a person of puzzling or contradictory character:
To me he has always been an enigma, one minute completely insensitive, the next moved to tears.
a saying, question, picture, etc., containing a hidden meaning; riddle.
(initial capital letter) a German-built enciphering machine developed for commercial use in the early 1920s and later adapted and appropriated by German and other Axis powers for military use through World War II.