The Collaborative International Dictionary of English v.0.48:

Shellac \Shel"lac`\, Shell-lac \Shell"-lac`\, n. [Shell + lac a
   resinous substance; cf. D. shellak, G. schellack.]
   1. Lac which has been reduced to a thin crust. See the Note
      under 2d Lac.
      [1913 Webster]

   2. A solution of shellac[1] in alcohol or other volatile
      solvent, used as a varnish.
      [PJC]

   3. A phonograph record, made of a material containing
      shellac; -- no longer manufactured. [Obsolescent] --RHUD
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Lac \Lac\, n. [Per. lak; akin to Skr. l[=a]ksh[=a]: cf. F.
   lague, It. & NL. lacca. Cf. Lake a color, Lacquer,
   Litmus.]
   A resinous substance produced mainly on the banyan tree, but
   to some extent on other trees, by the Laccifer lacca
   (formerly Coccus lacca), a scale-shaped insect, the female
   of which fixes herself on the bark, and exudes from the
   margin of her body this resinous substance.
   [1913 Webster]

   Note: Stick-lac is the substance in its natural state,
         incrusting small twigs. When broken off, and the
         coloring matter partly removed, the granular residuum
         is called seed-lac. When melted, and reduced to a
         thin crust, it is called shell-lac or shellac. Lac
         is an important ingredient in sealing wax, dyes,
         varnishes, and lacquers.
         [1913 Webster]

   Ceylon lac, a resinous exudation of the tree Croton
      lacciferum, resembling lac.

   Lac dye, a scarlet dye obtained from stick-lac.

   Lac lake, the coloring matter of lac dye when precipitated
      from its solutions by alum.

   Mexican lac, an exudation of the tree Croton Draco.
      [1913 Webster]

WordNet (r) 3.0 (2006):

shellac
    n 1: lac purified by heating and filtering; usually in thin
         orange or yellow flakes but sometimes bleached white
    2: a thin varnish made by dissolving lac in ethanol; used to
       finish wood [syn: shellac, shellac varnish]
    v 1: cover with shellac; "She wanted to shellac the desk to
         protect it from water spots" [syn: shellac, shellack]

Moby Thesaurus II by Grady Ward, 1.0:

77 Moby Thesaurus words for "shellac":
   apply paint, beat, bedaub, bedizen, begild, besmear, blank,
   brush on paint, bulldoze, calcimine, clobber, coat, color,
   complexion, cover, cream, dab, daub, deep-dye, defeat utterly, dip,
   distemper, double-dye, drub, dye, emblazon, enamel, engild, face,
   fast-dye, fresco, gild, glaze, gloss, grain, hue, illuminate,
   imbue, ingrain, japan, lacquer, lambaste, lay on color, lick,
   overbear, overwhelm, paint, parget, paste, pigment, prime, schmear,
   shade, shadow, shut out, skunk, slop on paint, smear, smother,
   snow under, stain, steamroller, stipple, thrash, tinct, tincture,
   tinge, tint, tone, trim, undercoat, varnish, wash, whelm,
   whitewash, whomp, whop