The Collaborative International Dictionary of English v.0.48:

Superiority \Su*pe`ri*or"i*ty\, n. [Cf. F. sup['e]riorit['e],
   LL. superioritas.]
   The quality, state, or condition of being superior; as,
   superiority of rank; superiority in merit.
   [1913 Webster]

   Syn: Preeminence; excellence; predominancy; prevalence;
        ascendency; odds; advantage.
        [1913 Webster]

WordNet (r) 3.0 (2006):

superiority
    n 1: the quality of being superior [syn: superiority, high
         quality] [ant: inferiority, low quality]
    2: the quality of being at a competitive advantage [syn:
       superiority, favorable position, favourable position]
    3: displaying a sense of being better than others; "he hated the
       white man's superiority and condescension"
    4: the state of excelling or surpassing or going beyond usual
       limits [syn: transcendence, transcendency, superiority]

Moby Thesaurus II by Grady Ward, 1.0:

207 Moby Thesaurus words for "superiority":
   aberrance, aberrancy, aberration, abnormality, abnormity, accent,
   advantage, advantageousness, agreeableness, amorphism, amperage,
   anomalism, anomalousness, anomaly, antecedence, antecedency,
   anteposition, anteriority, armipotence, ascendance, ascendancy,
   auspiciousness, authority, balance of power, beef, beneficialness,
   benevolence, benignity, black power, brute force, charge, charisma,
   class, clout, cogence, cogency, compulsion, concern, concernment,
   consequence, consequentiality, consideration, derangement, desert,
   deviation, difference, dint, distinction, divergence, dominance,
   dominancy, domination, dominion, drive, duress, eccentricity,
   effect, effectiveness, effectuality, eminence, eminent domain,
   emphasis, energy, erraticism, exaggeration, excellence, excess,
   expedience, fairness, favorableness, fineness, first-rateness,
   flower power, force, force majeure, forcefulness, front position,
   full blast, full force, goodliness, goodness, grace, greatness,
   healthiness, hegemony, helpfulness, heteromorphism, high order,
   high rank, import, importance, inferiority, influence,
   inimitability, interest, inundation, irregularity, kindness, lead,
   leadership, main force, main strength, mana, mark, matchlessness,
   materiality, merit, might, might and main, mightiness, moment,
   monstrosity, moxie, muscle power, niceness, note, overflowing,
   overgrowth, overlordship, overpass, overrun, overrunning,
   overspreading, paramountcy, peerlessness, pizzazz, pleasantness,
   poop, potence, potency, potentiality, power, power pack,
   power structure, power struggle, powerfulness, precedence,
   precedency, preceding, precession, precursor, predominance,
   predominancy, predomination, preeminence, preference, prefixation,
   prelude, preponderance, prepotence, prepotency, prestige, primacy,
   principality, priority, productiveness, productivity,
   profitableness, prominence, prothesis, puissance, pull, punch,
   push, quality, renown, rewardingness, self-importance,
   significance, sinew, skillfulness, soundness, sovereignty, steam,
   strength, stress, strong arm, subnormality, superpower, supremacy,
   surplus, suzerainship, suzerainty, teratism, the lead,
   top priority, unnaturalism, unnaturalness, upper hand, urgency,
   usefulness, validity, value, vehemence, victory, vigor, vim,
   virility, virtue, virtuousness, virulence, vitality, wattage,
   weight, whip hand, wholeness, worth