The Collaborative International Dictionary of English v.0.48:

Uniformity \U`ni*form"i*ty\, n. [L. uniformitas: cf. F.
   uniformit['e].]
   1. The quality or state of being uniform; freedom from
      variation or difference; resemblance to itself at all
      times; sameness of action, effect, etc., under like
      conditions; even tenor; as, the uniformity of design in a
      poem; the uniformity of nature.
      [1913 Webster]

   2. Consistency; sameness; as, the uniformity of a man's
      opinions.
      [1913 Webster]

   3. Similitude between the parts of a whole; as, the
      uniformity of sides in a regular figure; beauty is said to
      consist in uniformity with variety.
      [1913 Webster]

   4. Continued or unvaried sameness or likeness.
      [1913 Webster]

   5. Conformity to a pattern or rule; resemblance, consonance,
      or agreement; as, the uniformity of different churches in
      ceremonies or rites.
      [1913 Webster]

   Act of Uniformity (Eng. Hist.), an act of Parliament,
      passed in 1661, prescribing the form of public prayers,
      administration of sacraments, and other rites of the
      Established Church of England. Its provisions were
      modified by the "Act of Uniformity Amendment Act," of
      1872.
      [1913 Webster]

WordNet (r) 3.0 (2006):

uniformity
    n 1: a condition in which everything is regular and unvarying
    2: the quality of lacking diversity or variation (even to the
       point of boredom) [syn: uniformity, uniformness] [ant:
       nonuniformity]

Moby Thesaurus II by Grady Ward, 1.0:

221 Moby Thesaurus words for "uniformity":
   accommodation, accord, accordance, acquiescence, adaptation,
   adaption, adjustment, affinity, agreement, aplomb, arrangement,
   array, assent, balance, balanced personality, bilateral symmetry,
   ceaselessness, changelessness, chorus, clockwork regularity,
   coherence, coincidence, combination, compatibility, compliance,
   concert, concord, concordance, conformance, conformation,
   conformation other-direction, conformity, congeniality, congruence,
   congruency, congruity, consecutiveness, consistency, consonance,
   consort, constancy, constant flow, continualness, continuity,
   continuousness, conventionality, cool, cooperation, correspondence,
   deployment, disposal, disposition, downiness, drabness, dullness,
   dynamic symmetry, elementarity, endlessness, equality, equilibrium,
   equivalence, eurythmics, eurythmy, evenness, fastness,
   featurelessness, finish, firmness, flatness, flexibility,
   formation, frictionlessness, fullness, fundamentality, fusion,
   gaplessness, glabriety, glabrousness, glossiness, greasiness,
   harmoniousness, harmony, homeostasis, homogeneity, identity,
   imperturbability, incessancy, indiscernibility, indistinction,
   indistinctness, indistinguishableness, individuality,
   indivisibility, intactness, integrality, integration, integrity,
   intersection, invariability, inviolability, irreducibility,
   jointlessness, keeping, layout, levelness, line, lineup, lubricity,
   malleability, marshaling, methodicalness, monism, monotony,
   multilateral symmetry, nerve, obedience, observance, oiliness,
   oneness, order, organic unity, organization, orthodoxy, overlap,
   parallelism, particularity, peace, plainness, plenitude, pliancy,
   polarity, proportion, proportionality, punctuality, purity, quiet,
   quietude, rapport, reconcilement, reconciliation, regularity,
   reliability, repetition, rootedness, routine, sameness, sang-froid,
   satininess, seamlessness, secureness, security, self-consistency,
   selfsameness, setup, severity, shapeliness, silkiness, similarity,
   similitude, simpleness, simplicity, singleness, singularity,
   sleekness, slickness, slipperiness, smoothness, solidarity,
   solidification, solidity, soundness, stability, stable equilibrium,
   stable state, starkness, steadfastness, steadiness, steady nerves,
   steady state, strictness, structure, suavity, substantiality,
   successiveness, symmetricalness, symmetry, sync, synchronism,
   system, systematicalness, tally, tedium, timing, traditionalism,
   tranquillity, trilateral symmetry, unadulteration, unbrokenness,
   unchangeability, undeflectability, undifferentiation,
   undistinguishableness, undividedness, unification,
   unintermittedness, uninterruptedness, uninterruption, union,
   uniqueness, unison, unisonance, unity, univocity, unmixedness,
   unrelievedness, unshakable nerves, unshakableness,
   unsophistication, vagueness, velvetiness, wholeness