Source : Webster's Revised Unabridged Dictionary (1913)

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.

   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. -- {Su`per*la"tive*ly}, adv. --
      {Su`per*la"tive*ness}, n.

Source : WordNet®

superlatively
     adv : to a superlative degree