Source : Webster's Revised Unabridged Dictionary (1913)

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.

   2. To carry on a secret and illicit love or amour.

Source : WordNet®

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