capable of being shaped or bent or drawn out; "ductile copper"; "malleable metals such as gold"; "they soaked the leather to made it pliable"; "pliant molten glass"; "made of highly tensile steel alloy"
Literally, cabable of being worked by hammering, so that the material's shape can be extended by the application of mechanical force without breakage. This shape change should be permanent. Some materials must be heated to have this property. A more modern term is plasticity.