The Collaborative International Dictionary of English v.0.48:
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. [1913 Webster]WordNet (r) 3.0 (2006):
Frimaire n 1: third month of the Revolutionary calendar (November and December); the frosty month