Source : Webster's Revised Unabridged Dictionary (1913)

Nonce \Nonce\ (n[o^]ns), n. [For the nonce, OE. for the nones, a
   corruption of for then ones, where n. in then is a relic of
   AS. m in [eth]am, dat. of the article and demonstrative
   pronoun, E. the. See {For}, {Once}, and {The}.]
   The one or single occasion; the present call or purpose; --
   chiefly used in the phrase for the nonce.

         The miller was a stout carl for the nones. --Chaucer.

         And that he calls for drink, I 'll have prepared him A
         chalice for the nonce.                   --Shak.

   {Nonce word}, ``a word apparently employed only for the
      nonce''. --Murray (New English Dict.).

Source : WordNet®

nonce word
     n : a word with a special meaning used for a special occasion
         [syn: {hapax legomenon}]