Which term refers to worthless material that should be discarded?

The term "dross" specifically refers to the waste or impurities that remain after the valuable metal has been extracted, and it has evolved in common usage to signify anything considered worthless or of little value. In many contexts, particularly in metallurgy, it indicates material that is unwanted and should be removed to reveal what is useful or valuable beneath.

While "debris" can refer to scattered fragments or remains of something that has been destroyed, and "refuse" denotes waste or garbage, particularly organic matter, these terms do not encapsulate the concept of worthless material with the same specificity as "dross." "Waste" is a broader term that encompasses all unwanted material in various forms but does not carry the same connotation of being a byproduct of something valuable. Thus, "dross" is the most precise term for worthless material that should be discarded in contexts that involve refinement or extraction.