Thermidor (t?rmid?r) n (Historical Terms) the month of heat: the eleventh month of the French revolutionary calendar, extending from July 20 to Aug 18. Also: Fervidor [C19: from French, from Greek therm? heat + d?ron gift]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014