J5081850 (jo͞o′mär) n.A device used in ascending a fixed rope, having a springloaded cam that grips the rope when weight is applied but allows free movement upwards when the load is lifted. [Formerly a trademark.] ju′marv.
jumar
(ˈdʒuːmə) n (Mountaineering) Also called: jumar clamp a clamp with a handle that can move freely up a rope on which it is clipped but locks when downward pressure is appliedvb (intr) (Mountaineering) to climb up a fixed rope using jumars[C20: Swiss name]