The Collaborative International Dictionary of English v.0.48:

Varnish \Var"nish\, n. [OE. vernish, F. vernis, LL. vernicium;
   akin to F. vernir to varnish, fr. (assumed) LL. vitrinire to
   glaze, from LL. vitrinus glassy, fr. L. vitrum glass. See
   Vitreous.]
   [1913 Webster]
   1. A viscid liquid, consisting of a solution of resinous
      matter in an oil or a volatile liquid, laid on work with a
      brush, or otherwise. When applied the varnish soon dries,
      either by evaporation or chemical action, and the resinous
      part forms thus a smooth, hard surface, with a beautiful
      gloss, capable of resisting, to a greater or less degree,
      the influences of air and moisture.
      [1913 Webster]

   Note: According to the sorts of solvents employed, the
         ordinary kinds of varnish are divided into three
         classes: spirit, turpentine, and oil varnishes.
         --Encyc. Brit
         [1913 Webster]

   2. That which resembles varnish, either naturally or
      artificially; a glossy appearance.
      [1913 Webster]

            The varnish of the holly and ivy.     --Macaulay.
      [1913 Webster]

   3. An artificial covering to give a fair appearance to any
      act or conduct; outside show; gloss.
      [1913 Webster]

            And set a double varnish on the fame
            The Frenchman gave you.               --Shak.
      [1913 Webster]

   Varnish tree (Bot.), a tree or shrub from the juice or
      resin of which varnish is made, as some species of the
      genus Rhus, especially Rhus vernicifera of Japan. The
      black varnish of Burmah is obtained from the
      Melanorrh[oe]a usitatissima, a tall East Indian tree of
      the Cashew family. See Copal, and Mastic.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Varnish \Var"nish\, v. t. [imp. & p. p. Varnished; p. pr. &
   vb. n. Varnishing.] [Cf. F. vernir, vernisser. See
   Varnish, n.]
   [1913 Webster]
   1. To lay varnish on; to cover with a liquid which produces,
      when dry, a hard, glossy surface; as, to varnish a table;
      to varnish a painting.
      [1913 Webster]

   2. To cover or conceal with something that gives a fair
      appearance; to give a fair coloring to by words; to gloss
      over; to palliate; as, to varnish guilt. "Beauty doth
      varnish age." --Shak.
      [1913 Webster]

            Close ambition, varnished o'er with zeal. --Milton.
      [1913 Webster]

            Cato's voice was ne'er employed
            To clear the guilty and to varnish crimes.
                                                  --Addison.
      [1913 Webster]

WordNet (r) 3.0 (2006):

varnish
    n 1: a coating that provides a hard, lustrous, transparent
         finish to a surface
    v 1: cover with varnish [syn: varnish, seal]

Moby Thesaurus II by Grady Ward, 1.0:

277 Moby Thesaurus words for "varnish":
   acting, adorn, affectation, air brush, alibi, allow for, allowance,
   apology, appearance, apply paint, art paper, attitudinizing,
   becloud, bedaub, bedizen, befog, begild, belie, besmear, bias,
   blanket, blind, bluff, bluffing, brush, brush on paint, buff,
   burnish, calcimine, camera lucida, camera obscura, camouflage,
   canvas, chalk, charcoal, cheating, cloak, cloud, coat, coating,
   color, coloring, complexion, conceal, convolute, cover,
   cover story, cover up, cover-up, crayon, curtain, dab, daub,
   deception, decontamination, decorate, deep-dye, delusion, device,
   diminish, dip, disguise, dissemblance, dissemble, dissembling,
   dissimulation, distemper, distort, distract attention from,
   double-dye, drawing paper, drawing pencil, dress up, drier, dye,
   ease, easel, eclipse, elaborate, embellish, emblazon, embroider,
   enamel, engild, enrich, ensconce, enshroud, envelop, excuse,
   extenuate, extenuating circumstances, extenuation, extenuative,
   facade, face, facing, fakery, faking, false air, false front,
   false show, falsify, falsity, fast-dye, feigning, feint, festoon,
   film, finish, fixative, flourish, four-flushing, fraud, fresco,
   front, fudge, fur, furbish, garble, gild, gilding, gilt, glance,
   glaze, gloss, gloss over, grain, ground, guise, handle, hide, hue,
   humbug, humbuggery, ignore, illuminate, imbue, imposture, ingrain,
   involve, japan, keep under cover, lacquer, lame excuse, lay figure,
   lay on color, lessen, load with ornament, locus standi, luster,
   make allowance for, mask, masquerade, maulstick, medium,
   meretriciousness, mince, miscite, miscolor, misconstrue, misdirect,
   misinterpret, misquote, misrender, misreport, misrepresent,
   misstate, misuse, mitigate, mitigation, obfuscate, obscure, occult,
   ornament, ostensible motive, ostentation, outward show, overcharge,
   overlay, overload, overstate, paint, paintbrush, palette,
   palette knife, palliate, palliation, palliative, parget, pastel,
   pellicle, pencil, pervert, pigment, pigments, playacting, polish,
   poor excuse, pose, posing, posture, pretense, pretension, pretext,
   prime, protestation, public motive, put-off, qualification, refuge,
   representation, revetment, rub, scale, scour, scratchboard, screen,
   scum, seeming, semblance, shade, shadow, sham, shellac, shine,
   show, shroud, siccative, simulacrum, simulation, sketchbook,
   sketchpad, skin, slant, sleek, slick, slick down, slop on paint,
   slur over, smear, smoke screen, soft-pedal, soften, softening,
   spatula, speciousness, spray gun, stain, stalking-horse, stipple,
   strain, stratagem, stump, subterfuge, sugarcoat, tinct, tincture,
   tinge, tint, titivate, tone, torture, trick, trick out, twist,
   undercoat, understate, veil, veneer, warp, wash, wax, white,
   whiten, whitewash, whitewashing, window dressing