Pieces of copper. The definition of copper is of a reddish-brown, stretchable and metallic element, or something that is reddish-brown in color. An example of copper used as an adjective is in the phrase copper hair, which means reddish-brownish hair.opper-Computer Definition. A reddish-brown metallic element that is highly malleable, ductile, corrosion-resistant, and is an excellent conductor of electricity and heat. Only silver is a better conductor of electricity at room temperature.