The Collaborative International Dictionary of English v.0.48:

Nonpareil \Non`pa*reil"\, a. [F., from non not + pareil equal,
   fr. LL. pariculus, dim. of L. par equal. See Non, and
   Pair, Peer.]
   Having no equal; peerless.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Nonpareil \Non`pa*reil"\, n. [See Nonpareil, a. ]
   1. Something of unequaled excellence; a peerless thing or
      person; a nonesuch; -- often used as a name.
      [1913 Webster]

   2. [F. nonpareille.] (Print.) A size of type next smaller
      than minion and next larger than agate (or ruby).
      [1913 Webster]

   3. (Zool.)
      (a) A beautifully colored finch (Passerina ciris),
          native of the Southern United States. The male has the
          head and neck deep blue, rump and under parts bright
          red, back and wings golden green, and the tail bluish
          purple. Called also painted bunting and painted
          finch.
      (b) Any other similar bird of the same genus.
          [1913 Webster +PJC]

   4. (Cookery) A small sphere, less than 1 mm diamter, of
      colored sugar, used to decorate confections; -- usually
      used in the plural as though the name of a substance; as,
      sprinkled with nonpareils.
      [PJC]

   5. pl. A type of candy chocolate consisting of a small flat
      disk of chocolate, less than one inch diameter, having
      nonpareils[4] sprinkled on the top; as, she ate a box of
      nonpareils at the movie.
      [PJC]

WordNet (r) 3.0 (2006):

nonpareil
    adj 1: eminent beyond or above comparison; "matchless beauty";
           "the team's nonpareil center fielder"; "she's one girl in
           a million"; "the one and only Muhammad Ali"; "a peerless
           scholar"; "infamy unmatched in the Western world"; "wrote
           with unmatchable clarity"; "unrivaled mastery of her art"
           [syn: matchless, nonpareil, one(a), one and
           only(a), peerless, unmatched, unmatchable,
           unrivaled, unrivalled]
    n 1: model of excellence or perfection of a kind; one having no
         equal [syn: ideal, paragon, nonpareil, saint,
         apotheosis, nonesuch, nonsuch]
    2: colored beads of sugar used as a topping on e.g. candies and
       cookies
    3: a flat disk of chocolate covered with beads of colored sugar

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "nonpareil":
   A per se, ace, beau ideal, boss, champion, chief, choice, chosen,
   commander, cream, dean, elect, elite, exemplar, fat, flower,
   fugleman, genius, good example, head, higher-up, ideal, jewel,
   laureate, leader, man of men, master, mirror, model, ne plus ultra,
   nonesuch, optimum, paragon, pattern, phoenix, pick, prime,
   principal, prize, prodigy, queen, quintessence, ruler, select,
   senior, shining example, standard, star, superior, superlative,
   superman, superstar, the best, the best ever, the greatest,
   the most, the tops, the very best, top dog, virtuoso



The Free On-line Dictionary of Computing (30 December 2018):

Nonpareil

   One of five pedagogical languages based on Markov
   algorithms, used in ["Nonpareil, a Machine Level Machine
   Independent Language for the Study of Semantics", B. Higman,
   ULICS Intl Report No ICSI 170, U London (1968)].  The others
   were Brilliant, Diamond, Pearl and Ruby.