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]