dross

Things that are a total loss — really worthless or damaging — are dross. You could call that gunk between your teeth that comes out when you floss, dross. No one wants it, and it's harmful if it stays.

While dross is a noun for stuff that's physically left over or useless, like the nonmetallic stuff left when metal gets refined, it's also used for people and forms of art. A really bad movie can be called dross, and a low or despicable person can be dross. Debris, or trash, is another form of dross. "Searching the backyard for unexploded fireworks — the dross of Chinese New Year celebrations — was a tradition for the kids and a safeguard for the dogs."

Definitions of dross
1

n worthless or dangerous material that should be removed

Synonyms:
impurity
Type of:
waste, waste material, waste matter, waste product
any materials unused and rejected as worthless or unwanted

n the scum formed by oxidation at the surface of molten metals

Synonyms:
scoria, slag
Types:
basic slag
slag produced in making steel; low in silica but having large amounts of calcium phosphate; useful as fertilizer
Type of:
scum
a film of impurities or vegetation that can form on the surface of a liquid