hind limb: a posterior appendage such as a leg or the homologous structure in other animals
limb: one of the jointed appendages of an animal used for locomotion or grasping: arm; leg; wing; flipper
halon: a compound in which the hydrogen atoms of a hydrocarbon have been replaced by bromine and other halogen atoms; very stable; used in fire extinguishers although it is thought to release bromine that depletes the ozone layer