Source : Webster's Revised Unabridged Dictionary (1913)

Thermidor \Ther`mi`dor"\, n. [F., fr. Gr. ? warm, hot.]
   The eleventh month of the French republican calendar, --
   commencing July 19, and ending August 17. See the Note under
   {Vend['e]miaire}.

Source : WordNet®

Thermidor
     n : eleventh month of the Revolutionary calendar (July and
         August); the month of heat