The Collaborative International Dictionary of English v.0.48:

Whitewash \White"wash`\, v. t. [imp. & p. p. Whitewashed; p.
   pr. & vb. n. Whitewashing.]
   [1913 Webster]
   1. To apply a white liquid composition to; to whiten with
      whitewash.
      [1913 Webster]

   2. To make white; to give a fair external appearance to; to
      clear from imputations or disgrace; hence, to clear (a
      bankrupt) from obligation to pay debts.
      [1913 Webster]

   3. In various games, to defeat (an opponent) so that he fails
      to score, or to reach a certain point in the game; to
      skunk. [Colloq., U. S.]
      [Webster 1913 Suppl.]

   4. to gloss over or cover up (crimes or misfeasance).
      [PJC]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "whitewashing":
   albification, allowance, blanching, bleaching, calcimining,
   clobbering, coating, color, covering, crushing defeat,
   decisive defeat, decontamination, enameling, etiolation,
   extenuating circumstances, extenuation, extenuative, fresco,
   frosting, gilding, glazing, gloss, glossing, grizzling, japanning,
   mitigation, no contest, overwhelming defeat, painting, palliation,
   palliative, pasting, priming, qualification, shellacking,
   silvering, smashing defeat, smearing, softening, staining,
   stippling, total defeat, undercoating, utter defeat, varnish,
   varnishing, whitening, whitewash, whopping