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]

The Collaborative International Dictionary of English v.0.48:

Intrigue \In*trigue"\, v. t.
   To fill with artifice and duplicity; to complicate; to
   embarrass. [Obs.]
   [1913 Webster]

         How doth it [sin] perplex and intrique the whole course
         of your lives!                           --Dr. J.
                                                  Scott.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Intrigue \In*trigue"\, n. [Cf. F. intrique. See Intrigue, v.
   i.]
   [1913 Webster]
   1. Intricacy; complication. [Obs.] --Sir M. Hale.
      [1913 Webster]

   2. A complicated plot or scheme intended to effect some
      purpose by secret artifice; conspiracy; stratagem.
      [1913 Webster]

            Busy meddlers with intrigues of state. --Pomfret.
      [1913 Webster]

   3. The plot of a play or romance; a complicated scheme of
      designs, actions, and events. --Pope.
      [1913 Webster]

   4. A secret and illicit love affair between two persons of
      different sexes; an amour; a liaison.
      [1913 Webster]

            The hero of a comedy is represented victorious in
            all his intrigues.                    --Swift.

   Syn: Plot; scheme; conspiracy; machination.
        [1913 Webster]

WordNet (r) 3.0 (2006):

intrigue
    n 1: a crafty and involved plot to achieve your (usually
         sinister) ends [syn: intrigue, machination]
    2: a clandestine love affair
    v 1: cause to be interested or curious [syn: intrigue,
         fascinate]
    2: form intrigues (for) in an underhand manner [syn: scheme,
       intrigue, connive]

Moby Thesaurus II by Grady Ward, 1.0:

178 Moby Thesaurus words for "intrigue":
   Byzantine intrigues, absorb, adulterous affair, adultery, affair,
   amor, amour, angle, appeal, art, artful dodge, artfulness,
   artifice, attract, backstairs influence, becharm, beguile, bewitch,
   blind, brew, cabal, captivate, carry away, cast a spell, charm,
   chicanery, cogitate, collogue, collude, collusion, complicity,
   complot, concoct, confederacy, connections, connivance, connive,
   conspiracy, conspire, contrivance, contrive, contriving, cook up,
   countermine, counterplot, coup, covin, craft, craftiness,
   credibility gap, cuckoldry, cute trick, deals, deceit,
   deceitfulness, deception, deep-laid plot, design, device, devise,
   disingenuousness, dodge, double-dealing, enchant, engineer,
   engineering, enrapture, enravish, entanglement, enthrall, entrance,
   eternal triangle, excite, expedient, fakement, falseheartedness,
   fascinate, feint, fetch, finagle, finagling, finesse, flirtation,
   forbidden love, forswearing, frame, frame up, frame-up, fraud,
   gambit, game, games, gerrymander, gimmick, grift, guile,
   hanky-panky, hatch, hatch a plot, hatch up, hypnotize,
   illicit love, infatuate, infidelity, influence peddling,
   insincerity, interest, intimacy, intrigues, jockey, jugglery,
   knavery, lay a plot, liaison, little game, lobbying, lobbyism,
   love affair, machinate, machination, maneuver, maneuvering,
   manipulate, manipulation, mesmerize, move, operate, perjury, pique,
   play games, plot, plotting, ploy, ploys, practice, pull strings,
   racket, red herring, rig, rigging, romance, romantic tie, ropes,
   ruse, scheme, schemery, schemes, scheming, sharp practice, shift,
   sleight, spell, spellbind, stratagem, strategy, strings,
   subterfuge, tactic, titillate, transport, triangle, trick,
   trickery, uncandidness, uncandor, underplot, unfaithfulness,
   unfrankness, unsincereness, untruthfulness, vamp, wangle,
   web of intrigue, wile, wily device, wire-pulling, wires, witch