The Collaborative International Dictionary of English v.0.48:

Tortuous \Tor"tu*ous\, a. [OE. tortuos, L. tortuosus, fr. tortus
   a twisting, winding, fr. torquere, tortum, to twist: cf. F.
   tortueux. See Torture.]
   1. Bent in different directions; wreathed; twisted; winding;
      as, a tortuous train; a tortuous leaf or corolla.
      [1913 Webster]

            The badger made his dark and tortuous hole on the
            side of every hill where the copsewood grew thick.
                                                  --Macaulay.
      [1913 Webster]

   2. Fig.: Deviating from rectitude; indirect; erroneous;
      deceitful.
      [1913 Webster]

            That course became somewhat lesstortuous, when the
            battle of the Boyne had cowed the spirit of the
            Jakobites.                            --Macaulay.
      [1913 Webster]

   3. Injurious: tortious. [Obs.]
      [1913 Webster]

   4. (Astrol.) Oblique; -- applied to the six signs of the
      zodiac (from Capricorn to Gemini) which ascend most
      rapidly and obliquely. [Obs.] --Skeat.
      [1913 Webster]

            Infortunate ascendent tortuous.       --Chaucer.
      [1913 Webster] --Tor"tu*ous*ly, adv. --
      Tor"tu*ous*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tortuousness
    n 1: a tortuous and twisted shape or position; "they built a
         tree house in the tortuosities of its boughs"; "the acrobat
         performed incredible contortions" [syn: tortuosity,
         tortuousness, torsion, contortion, crookedness]
    2: puzzling complexity [syn: complicatedness, complication,
       knottiness, tortuousness]