Definition
Scummy means covered in scum or resembling scum. Scum is a layer of dirt or froth on top of a liquid, often unpleasant. It can also describe something morally reprehensible or disgusting. It implies something is of low quality or is morally tainted. Think of a stagnant pond with a green layer on top β that's scummy. It's more than just dirty; it's gross and potentially harmful.