Source : Webster's Revised Unabridged Dictionary (1913)

Enigma \E*nig"ma\, n.; pl. {Enigmas}. [L. aenigma, Gr. ?, fr. ?
   to speak darkly, fr. ? tale, fable.]
   1. A dark, obscure, or inexplicable saying; a riddle; a
      statement, the hidden meaning of which is to be discovered
      or guessed.

            A custom was among the ancients of proposing an
            enigma at festivals.                  --Pope.

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