The Collaborative International Dictionary of English v.0.48:

Smear \Smear\ (sm[=e]r), v. t. [imp. & p. p. Smeared
   (sm[=e]rd); p. pr. & vb. n. Smearing.] [OE. smeren,
   smerien, AS. smierwan, smyrwan, fr. smeoru fat, grease; akin
   to D. smeren, OHG. smirwen, G. schmieren, Icel. smyrja to
   anoint. See Smear, n.]
   1. To overspread with anything unctuous, viscous, or
      adhesive; to daub; as, to smear anything with oil. "Smear
      the sleepy grooms with blood." --Shak.
      [1913 Webster]

   2. To soil in any way; to contaminate; to pollute; to stain
      morally; as, to be smeared with infamy. --Shak.
      [1913 Webster]

   3. To smudge, blur, or render indistinct (writing, pictures,
      etc.).
      [PJC]

   4. to vilify (a person); to damage (a person's reputation),
      especially falsely or by unfair innuendo, and with
      malicious intent.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Smear \Smear\, n. [OE. smere,. smeoru fat, grease; akin to D.
   smeer, G. schmeer, OHG. smero, Icel. smj["o]r, Sw. & Dan.
   sm["o]r butter, Goth. sma['i]r[thorn]r fatness, smarna dung;
   cf. Lith. smarsas fat. Cf. Smirch.]
   1. A fat, oily substance; oinment. --Johnson.
      [1913 Webster]

   2. Hence, a spot made by, or as by, an unctuous or adhesive
      substance; a blot or blotch; a daub; a stain.
      [1913 Webster]

            Slow broke the morn,
            All damp and rolling vapor, with no sun,
            But in its place a moving smear of light.
                                                  --Alexander
                                                  Smith.
      [1913 Webster]

WordNet (r) 3.0 (2006):

smear
    n 1: slanderous defamation [syn: smear, vilification,
         malignment]
    2: a thin tissue or blood sample spread on a glass slide and
       stained for cytologic examination and diagnosis under a
       microscope [syn: smear, cytologic smear, cytosmear]
    3: a blemish made by dirt; "he had a smudge on his cheek" [syn:
       smudge, spot, blot, daub, smear, smirch, slur]
    4: an act that brings discredit to the person who does it; "he
       made a huge blot on his copybook" [syn: blot, smear,
       smirch, spot, stain]
    v 1: stain by smearing or daubing with a dirty substance
    2: make a smudge on; soil by smudging [syn: smear, blur,
       smudge, smutch]
    3: cover (a surface) by smearing (a substance) over it; "smear
       the wall with paint"; "daub the ceiling with plaster" [syn:
       daub, smear]
    4: charge falsely or with malicious intent; attack the good name
       and reputation of someone; "The journalists have defamed me!"
       "The article in the paper sullied my reputation" [syn:
       defame, slander, smirch, asperse, denigrate,
       calumniate, smear, sully, besmirch]

Moby Thesaurus II by Grady Ward, 1.0:

228 Moby Thesaurus words for "smear":
   anoint, apply paint, asperse, aspersion, attack, attaint,
   badge of infamy, bar sinister, baton, beat, bedaub, bedizen,
   beeswax, befoul, begild, begrime, bend sinister, besmear, besmirch,
   besmoke, besmutch, besoil, bespatter, bestain, black, black eye,
   black mark, blacken, blackening, blank, bloodstain, blot, blotch,
   blow upon, blur, brand, broad arrow, brush on paint, bulldoze,
   butter, calcimine, call names, calumniate, calumny, censure,
   champain, character assassination, clobber, coat, color,
   complexion, cover, cream, dab, darken, daub, deep-dye, defamation,
   defamation of character, defame, defeat utterly, defile,
   defilement, denigrate, denigration, dip, dirty, disapprove,
   discolor, discredit, disparage, disparagement, distemper,
   double-dye, dress, drub, dye, emblazon, embrocate, enamel,
   engage in personalities, engild, expose, expose to infamy, eyesore,
   face, fast-dye, fleck, flick, flyspeck, foil, fresco, frustrate,
   gibbet, gild, glaze, gloss, glycerolate, grain, grease,
   grease the wheels, hang in effigy, heap dirt upon, hue, illuminate,
   imbue, imputation, ingrain, japan, lacquer, lambaste, lard, lay on,
   lay on color, libel, lick, lubricate, macula, maculation, macule,
   malicious defamation, mark, mark of Cain, muckrake, muckraking,
   mudslinging, name-calling, oil, onus, overbear, overlay,
   overspread, overwhelm, paint, parget, paste, patch, pigment,
   pillory, pillorying, plaster, point champain, pomade, prime,
   reflection, reprimand, reproach, repulse, revile, revilement, rub,
   salve, scandal, scandalize, schmear, scorch, sear, shade, shadow,
   shellac, shut out, singe, skunk, slander, slap on, slather, slick,
   slick on, slop on paint, slubber, slur, smear campaign, smear on,
   smear word, smirch, smoke, smooth the way, smother, smouch, smudge,
   smut, smutch, snow under, soap the ways, soil, soilage, soilure,
   spatter, speck, speckle, splash, splatter, splotch, spot, spread,
   spread on, spread with, stain, steamroller, stigma, stigmatism,
   stigmatization, stigmatize, stipple, sully, taint, tar, tarnish,
   thrash, throw mud at, tinct, tincture, tinge, tint, tone, trim,
   undercoat, unguent, varnish, vilification, vilify, wash, wax,
   whelm, whitewash, whomp, whop, wipe