The Collaborative International Dictionary of English v.0.48:

Enigmatic \E`nig*mat"ic\ (?; 277), Enigmatical
\E`nig*mat"ic*al\, a. [Cf. F. ['e]nigmatique.]
   Relating to or resembling an enigma; not easily explained or
   accounted for; darkly expressed; not clear to the
   understanding; obscure; puzzling; as, an enigmatical answer;
   I didn't grasp the meaning of that enigmatical comment until
   much later; prophetic texts so enigmatical that their meaning
   has been disputed for centuries.

   Syn: dark, obscure, puzzling.
        [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

enigmatic
    adj 1: not clear to the understanding; "I didn't grasp the
           meaning of that enigmatic comment until much later";
           "prophetic texts so enigmatic that their meaning has been
           disputed for centuries" [syn: enigmatic, enigmatical,
           puzzling]
    2: resembling an oracle in obscurity of thought; "the oracular
       sayings of Victorian poets"; "so enigmatic that priests might
       have to clarify it"; "an enigmatic smile" [syn: enigmatic,
       oracular]

Moby Thesaurus II by Grady Ward, 1.0:

123 Moby Thesaurus words for "enigmatic":
   able, ambiguous, amphibological, amphibolous, arcane, baffling,
   beguiling, bewildering, bothering, cabalistic, censored,
   classified, close, closed, concealed, confounding, confusing,
   cryptic, dark, discomposing, disconcerting, dismaying, distracting,
   disturbing, embarrassing, equivocal, equivocatory, esoteric,
   exceptional, extraordinary, fabulous, fantastic, fascinating,
   hermetic, hidden, hush-hush, incalculable, incognizable,
   incomprehensible, inconceivable, incredible, intricate, ironic,
   latent, marvelous, miraculous, multivocal, mysterious, mystifying,
   obscure, occult, outlandish, passing strange, perplexing,
   perturbing, phenomenal, polysemantic, polysemous, problematic,
   prodigious, puzzling, rare, remarkable, restricted, riddling,
   sealed, secret, sensational, smothered, sphinxlike, stifled,
   strange, striking, stupendous, suppressed, top secret, ulterior,
   unapparent, unapprehended, unascertained, unbeknown, unbreatheable,
   uncertain, uncharted, unclassified, under security, under wraps,
   undisclosable, undisclosed, undiscoverable, undiscovered,
   undivulgable, undivulged, unexplained, unexplored, unexposed,
   unfamiliar, unfathomed, unheard, unheard-of, unidentified,
   unimaginable, uninvestigated, unique, unknowable, unknown,
   unperceived, unplumbed, unprecedented, unrevealable, unrevealed,
   unspoken, unsuspected, untellable, untold, untouched, unutterable,
   unuttered, unwhisperable, upsetting, virgin, wonderful, wondrous