An indicator of extreme weather or temperature, typically the cold. It is usually used with the qualifier "enough," a verb, and some physical appendage of the monkey, most commonly in the semi-vulgar phrase, "cold enough to freeze the balls (testes) off a brass monkey." After that blizzard set in, it became cold enough to freeze the balls off a brass monkey.Gosh, it's hot enough out here to melt the ears off a brass monkey.