The Collaborative International Dictionary of English v.0.48:

briquet \bri*quet"\, Briquette \Bri*quette"\, n. [Also
   briquet.] [F., dim. of brique brick.]
   1. A block of compacted charcoal, coal dust, or peat, etc.,
      used as a fuel. Charcoal briquettes are a common fuel used
      for the outdoor barbecue grill.
      [Webster 1913 Suppl. +PJC]

   2. A block of artificial stone in the form of a brick, used
      for paving; also, a molded sample of solidified cement or
      mortar for use as a test piece for showing the strength of
      the material.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

briquet
    n 1: a block made from charcoal or coal dust and burned as fuel
         [syn: briquette, briquet]