Source : Webster's Revised Unabridged Dictionary (1913)

Frimaire \Fri"maire`\, n. [F., fr. frimas hoarfrost.]
   The third month of the French republican calendar. It
   commenced November 21, and ended December 20., See
   {Vend['e]miaire}.

Source : WordNet®

Frimaire
     n : third month of the Revolutionary calendar (November and
         December); the frosty month