Source : Webster's Revised Unabridged Dictionary (1913)

Nonesuch \None"such`\, n.
   A person or thing of a sort that there is no other such;
   something extraordinary; a thing that has not its equal. It
   is given as a name to various objects, as to a choice variety
   of apple, a species of medic ({Medicago lupulina}), a variety
   of pottery clay, etc.

Source : WordNet®

nonesuch
     n : model of excellence or perfection of a kind; one having no
         equal [syn: {ideal}, {paragon}, {nonpareil}, {saint}, {apotheosis},
          {nonsuch}]