Jumar: a mechanical device generically referred to as an "ascender" that attaches to the rope and can only slide up, not down, ie, it "ascends" the rope. This term is used even to refer to other brands of similar devices, such as the one by Petzl. The term "to jumar" means to ascend a rope by means of ascenders. The slang term is "to jug", as in, "He completed the lead in two hours, but I jugged it in 15 minutes."

Jumar brand ascender		Petzl brand ascender