The Collaborative International Dictionary of English v.0.48:

Disingenuous \Dis`in*gen"u*ous\, a.
   1. Not noble; unbecoming true honor or dignity; mean;
      unworthy; as, disingenuous conduct or schemes.
      [1913 Webster]

   2. Not ingenuous; wanting in noble candor or frankness; not
      frank or open; uncandid; unworthily or meanly artful.
      [1913 Webster]

            So disingenuous as not to confess them [faults].
                                                  --Pope.
      -- Dis`in*gen"u*ous*ly, adv. --T. Warton. --
      Dis`in*gen"u*ous*ness, n. --Macaulay.
      [1913 Webster]

WordNet (r) 3.0 (2006):

disingenuous
    adj 1: not straightforward or candid; giving a false appearance
           of frankness; "an ambitious, disingenuous, philistine,
           and hypocritical operator, who...exemplified...the most
           disagreeable traits of his time"- David Cannadine; "a
           disingenuous excuse" [syn: disingenuous, artful]
           [ant: artless, ingenuous]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "disingenuous":
   apparently sound, artful, calculating, casuistic, clever,
   colorable, contriving, crafty, cunning, deceitful, deceptive,
   designing, devious, dishonest, double-dealing, duplicitous, empty,
   fallacious, false, falsehearted, feigned, forsworn, foxy, guileful,
   hollow, hypocritical, illusive, indirect, insidious, insincere,
   jesuitic, left-handed, mealymouthed, oblique, overrefined,
   oversubtle, perjured, philosophistic, plausible, plotting,
   scheming, shifty, slick, sly, smooth, sophistic, sophistical,
   specious, tongue in cheek, tricky, two-faced, uncandid,
   underhanded, unfrank, unserious, unsincere, untruthful, wily