dross

Things that are a total loss — really worthless or damaging — are dross. That gunk between your teeth that comes out when you floss? You could call that 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