The Collaborative International Dictionary of English v.0.48:

Intrigue \In*trigue"\ ([i^]n*tr[=e]g"), v. i. [imp. & p. p.
   Intrigued (-tr[=e]gd"); p. pr. & vb. n. Intriguing.] [F.
   intriguer, OF. intriquer, entriquer; cf. It. intrigare. See
   Intricate, Extricate.]
   1. To form a plot or scheme; to contrive to accomplish a
      purpose by secret artifice.
      [1913 Webster]

   2. To carry on a secret and illicit love or amour.
      [1913 Webster]

WordNet (r) 3.0 (2006):

intriguing
    adj 1: disturbingly provocative; "an intriguing smile" [syn:
           challenging, intriguing]
    2: capable of arousing interest or curiosity; "our team came up
       with some most intriguing finds"

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "intriguing":
   Byzantine, Machiavellian, alluring, appealing, appetizing,
   attractive, beguiling, bewitching, blandishing, cajoling,
   calculating, captivating, catching, charismatic, charming, coaxing,
   collusive, come-hither, connivent, conniving, conspiring,
   contriving, coquettish, delightful, designing, enchanting,
   engaging, enravishing, enthralling, enticing, entrancing, exciting,
   exotic, exquisite, fascinating, fetching, flirtatious, glamorous,
   heart-robbing, hypnotic, interesting, inviting, irresistible,
   lovely, luxurious, mesmeric, mouth-watering, piquant, plotting,
   prepossessing, provocative, provoquant, ravishing, scheming,
   seducing, seductive, sensuous, siren, sirenic, spellbinding,
   spellful, stratagemical, taking, tantalizing, teasing, tempting,
   thrilling, tickling, titillating, titillative, up to, voluptuous,
   winning, winsome, witching