The Collaborative International Dictionary of English v.0.48:

enigma \e*nig"ma\ ([-e]*n[i^]g"m[.a]), n.; pl. enigmas
   ([-e]*n[i^]g"m[.a]z). [L. aenigma, Gr. a'i`nigma, fr.
   a'ini`ssesqai to speak darkly, fr. a'i^nos tale, fable.]
   1. A dark, obscure, or inexplicable saying; a riddle; a
      statement, the hidden meaning of which is to be discovered
      or guessed.
      [1913 Webster]

            A custom was among the ancients of proposing an
            enigma at festivals.                  --Pope.
      [1913 Webster]

   2. An action, mode of action, or thing, which cannot be
      satisfactorily explained; a puzzle; as, his conduct is an
      enigma. Enigmatic

WordNet (r) 3.0 (2006):

enigma
    n 1: something that baffles understanding and cannot be
         explained; "how it got out is a mystery"; "it remains one
         of nature's secrets" [syn: mystery, enigma, secret,
         closed book]
    2: a difficult problem [syn: riddle, conundrum, enigma,
       brain-teaser]

Moby Thesaurus II by Grady Ward, 1.0:

99 Moby Thesaurus words for "enigma":
   Chinese puzzle, Gordian knot, arcanum, baffle, bafflement,
   baffling problem, bewilderment, bother, brain twister, cabala,
   classified information, confidence, confidential communication,
   confoundment, confusion, conundrum, crossword puzzle, crux,
   dark horse, dilemma, discomposure, disconcert, disconcertedness,
   disconcertion, disconcertment, disturbance, embarrassment,
   enigmatic question, esoterica, fix, floorer, frontier,
   frontiers of knowledge, guarded secret, hermetics, jam,
   jigsaw puzzle, knot, knotty point, matter of ignorance,
   mind-boggler, mystery, mystery of mysteries, mystification, n,
   node, nodus, nonplus, nut to crack, oxymoron, paradox,
   perplexed question, perplexity, personal matter, perturbation,
   pickle, plight, pons asinorum, poser, pother, predicament,
   private matter, privileged communication, privity, problem,
   profound secret, puzzle, puzzlement, puzzler, quandary, question,
   question mark, restricted information, riddle, scrape, sealed book,
   secret, sixty-four dollar question, stew, sticker, stumper, teaser,
   terra incognita, the incalculable, the occult, the strange,
   the unfamiliar, the unknowable, the unknown, tough proposition,
   unassuredness, unexplored ground, unexplored territory,
   unknown quantity, upset, vexed question, why, x, z



The Free On-line Dictionary of Computing (30 December 2018):

Enigma

    The electro-mechanical cipher
   engine used by the Germans in World War II to encrypt and
   decrypt field orders.  Many of their messages were deciphered
   at Bletchley Park, by Alan Turing and others.

   See also: Tunny Emulator.

   (2012-03-25)


U.S. Gazetteer Places (2000):

Enigma, GA -- U.S. town in Georgia
   Population (2000):    869
   Housing Units (2000): 348
   Land area (2000):     3.251680 sq. miles (8.421811 sq. km)
   Water area (2000):    0.032409 sq. miles (0.083940 sq. km)
   Total area (2000):    3.284089 sq. miles (8.505751 sq. km)
   FIPS code:            27596
   Located within:       Georgia (GA), FIPS 13
   Location:             31.411466 N, 83.331056 W
   ZIP Codes (1990):     31749
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Enigma, GA
    Enigma