The Collaborative International Dictionary of English v.0.48:

Semblance \Sem"blance\, n. [F. See Semblable, a.]
   1. Seeming; appearance; show; figure; form.
      [1913 Webster]

            Thier semblance kind, and mild their gestures were.
                                                  --Fairfax.
      [1913 Webster]

   2. Likeness; resemblance, actual or apparent; similitude; as,
      the semblance of worth; semblance of virtue.
      [1913 Webster]

            Only semblances or imitations of shells. --Woodward.
      [1913 Webster]

WordNet (r) 3.0 (2006):

semblance
    n 1: an outward or token appearance or form that is deliberately
         misleading; "he hoped his claims would have a semblance of
         authenticity"; "he tried to give his falsehood the gloss of
         moral sanction"; "the situation soon took on a different
         color" [syn: semblance, gloss, color, colour]
    2: an erroneous mental representation [syn: illusion,
       semblance]
    3: picture consisting of a graphic image of a person or thing
       [syn: likeness, semblance]

Moby Thesaurus II by Grady Ward, 1.0:

215 Moby Thesaurus words for "semblance":
   Prospero, accordance, acting, affectation, affinity, agreement,
   air, airiness, alibi, alikeness, alliance, analogy, angle, aping,
   apology, appearance, approach, approximation, aspect, assimilation,
   atmosphere, attitudinizing, aura, blind, bluff, bluffing,
   certified copy, cheating, cloak, closeness, color, coloring,
   community, companion, comparability, comparison, configuration,
   conformity, copy, copying, correspondence, counterfeit, cover,
   cover story, cover-up, dead ringer, deception, delusion,
   delusiveness, device, disguise, dissemblance, dissembling,
   dissimulation, double, duplicate, ectype, effect, effigy, eidolon,
   exact likeness, excuse, facade, face, facet, fair copy,
   faithful copy, fake, fakery, faking, fallaciousness, false air,
   false appearance, false front, false light, false show, falseness,
   falsity, fashion, feature, feel, feeling, feigning, feint, fellow,
   figure, forgery, form, four-flushing, fraud, front, gestalt, gilt,
   gloss, guise, handle, humbug, humbuggery, icon, idealization,
   identity, idol, illusionism, illusionist, illusiveness, image,
   imago, imitation, immateriality, imposture, impression,
   lame excuse, light, likeness, likening, lineaments, living image,
   living picture, locus standi, look, magic, magic act, magic show,
   magician, manner, mask, masquerade, match, mate, meretriciousness,
   metaphor, mimicking, miniature, mirroring, model, mood, nearness,
   ostensible motive, ostentation, outward show, parallelism, parity,
   pasticcio, pastiche, phase, phasis, phony, photograph, picture,
   playacting, poor excuse, portrait, pose, posing, posture,
   prestidigitation, pretense, pretension, pretext, protestation,
   public motive, put-off, reference, reflection, refuge, regard,
   representation, resemblance, respect, rubbing, sameness, screen,
   seeming, shadow, sham, shape, show, showing, side, similarity,
   simile, similitude, simulacrum, simulation, slant, sleight of hand,
   smoke screen, sorcerer, sorcery, specious appearance, speciousness,
   spit and image, spitting image, stalking-horse, stratagem, style,
   subterfuge, total effect, trace, tracing, trick, twin, twist,
   unactuality, unreality, unsubstantiality, varnish, veil, veneer,
   very image, very picture, view, viewpoint, window dressing, wise