scummy Definition

scum
noun

1. Dirt or waste matter floating on the surface of a liquid, especially in the form of foam or froth.

Thesaurus: residue, froth, film, flotsam, crust, dregs, dross, spume.
2. colloq, derog
A worthless or contemptible person or such people.
Thesaurus: rabble, mob, riff-raff, pariah; Antonym: elite, aristocracy.

verb scummed, scumming

1. To remove the scum from (a liquid).
intr
2. To form or throw up a scum.

Derivative: scummer
noun

Derivative: scummy
adj

Etymology: 13c: from Dutch schum foam.