The Collaborative International Dictionary of English v.0.48:

Superlative \Su`per*la"tive\, n.
   1. That which is highest or most eminent; the utmost degree.
      [1913 Webster]

   2. (Gram.)
      (a) The superlative degree of adjectives and adverbs;
          also, a form or word by which the superlative degree
          is expressed; as, strongest, wisest, most stormy,
          least windy, are all superlatives.
          [1913 Webster]

   Absolute superlative, a superlative in an absolute rather
      than in a comparative or exclusive sense. See Elative.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Superlative \Su`per*la"tive\, a. [L. superlativus, fr.
   superlatus excessive, used as p. p. of superiorferre, but
   from a different root: cf. F. superlatif. See Elate,
   Tolerate.]
   1. Lifted up to the highest degree; most eminent; surpassing
      all other; supreme; as, superlative wisdom or prudence; a
      woman of superlative beauty; the superlative glory of the
      divine character.
      [1913 Webster]

   2. (Gram.) Expressing the highest or lowest degree of the
      quality, manner, etc., denoted by an adjective or an
      adverb. The superlative degree is formed from the positive
      by the use of -est, most, or least; as, highest, most
      pleasant, least bright.
      [1913 Webster] -- Su`per*la"tive*ly, adv. --
      Su`per*la"tive*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

superlative
    adj 1: highest in quality [syn: greatest, sterling(a),
           superlative]
    n 1: an exaggerated expression (usually of praise); "the critics
         lavished superlatives on it"
    2: the highest level or degree attainable; the highest stage of
       development; "his landscapes were deemed the acme of beauty";
       "the artist's gifts are at their acme"; "at the height of her
       career"; "the peak of perfection"; "summer was at its peak";
       "...catapulted Einstein to the pinnacle of fame"; "the summit
       of his ambition"; "so many highest superlatives achieved by
       man"; "at the top of his profession" [syn: acme, height,
       elevation, peak, pinnacle, summit, superlative,
       meridian, tiptop, top]
    3: the superlative form of an adjective or adverb; "`fastest' is
       the superlative of the adjective `fast'"; "`least famous' is
       the superlative degree of the adjective `famous'"; "`most
       surely' is the superlative of the adverb `surely'" [syn:
       superlative, superlative degree]

Moby Thesaurus II by Grady Ward, 1.0:

215 Moby Thesaurus words for "superlative":
   Olympian, absolute, accomplished, ace, aerial, aggrandized,
   aggrandizement, airy, altitudinous, amplification, amplified,
   arrant, ascending, aspiring, ballyhoo, ballyhooed, best, big talk,
   blowing up, burlesque, capital, caricature, champion, choice,
   chosen, classical, colossal, complete, consummate, crack, crass,
   cream, dazzling, decided, definitive, dilatation, dilation,
   disproportionate, dominating, downright, egregious, elect,
   elevated, elite, eminent, enhancement, enlargement, ethereal,
   exaggerated, exaggerating, exaggeration, exalted, excellent,
   exceptional, excess, excessive, exorbitance, exorbitant, expansion,
   extraordinary, extravagance, extravagant, extreme, fantastic, fat,
   finest, finished, first-class, first-rate, flagrant, flower,
   glaring, grandiloquence, grandiloquent, great, greatest, gross,
   haughty, heightening, high, high-flown, high-pitched,
   high-reaching, high-set, high-up, highest, huckstering, hyperbole,
   hyperbolic, hyperbolism, incomparable, inflated, inflation,
   inordinacy, inordinate, intolerable, lofty, magnification,
   magnificent, magnified, matchless, maximal, maximum, monumental,
   most, mounting, nonesuch, nonpareil, optimum, out-and-out,
   outright, outstanding, outtopping, overdone, overdrawn,
   overemphasis, overemphasized, overemphatic, overestimated,
   overestimation, overgreat, overkill, overlarge, overlooking,
   overpraised, oversold, overstated, overstatement, overstressed,
   overtopping, overwrought, paragon, paramount, peerless, perfect,
   pick, positive, precious, prime, prize, prodigal, prodigality,
   profound, profuse, profuseness, prominent, pronounced, proper,
   puffed, puffery, puffing up, queen, quintessence, rank, regular,
   select, sensationalism, shattering, shocking, singular, smashing,
   soaring, spectacular, spiring, stark, stark-staring, steep,
   sterling, stretched, stretching, sublime, super, superb,
   superexcellent, superior, supernal, supreme, surpassing, tall talk,
   terrific, the best, the best ever, the tops, the veriest,
   the very best, thorough, thoroughgoing, tip-top, top, top-notch,
   topless, toplofty, topmost, topping, total, touted, touting,
   towering, towery, travesty, unbearable, unconscionable, undeniable,
   unequivocal, unique, unmitigated, unqualified, unrelieved,
   unspoiled, unsurpassed, uplifted, uppermost, upreared, utmost,
   utter