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]