. | 1. | a puzzling or inexplicable occurrence or situation: His disappearance is an enigma that has given rise to much speculation. |
| 2. | a person of puzzling or contradictory character: To me he has always been an enigma, one minute completely insensitive, the next moved to tears. |
| 3. | a saying, question, picture, etc., containing a hidden meaning; riddle. |
| 4. | (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. |

Enigma hardware, cryptography
The electro-mechanical cipher engine used by the Germans in World War II. Many of their messages were deciphered at Bletchley Park, by Alan Turing and others.
(2000-09-30)