Cupro is a fibre made from cellulose, by combine the compound with copper and ammonia. The cellulose is placed into a solution of copper and ammonia, which dissolves the cellulose. This mixture is hardened and then spun into thin fibres. The most important features of cupro are a soft touch and high absorbability. These textiles are often used for elegant dresses, blouses, and pants.
You can find more information about Cupro (CU) in Wikipedia.