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Meaning of billon

bil•lon

Pronunciation: (bil'un), [key]
— n.
  1. an alloy used in coinage, consisting of gold or silver with a larger amount of base metal.
  2. an alloy of silver with copper or the like, used for coins of small denomination.
  3. any coin struck from such an alloy.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.