1. slang An offensive, detestable, repellent person, especially one who does unscrupulous or immoral things. Sometimes spelled as one word. My last boss was a total sludge ball, making all sorts of shady deals to skim a bit of extra profit for herself. That sludge ball defrauded his clients for millions of dollars. They ought to lock him up and throw away the key.

2. slang A ball-like object, resembling a stone or tumorous mass, formed from biliary sludge. The term typically refers to its appearance in ultrasound scans. They were worried I might have gallbladder cancer, but a second ultrasound showed the mass to be nothing more than a sludge ball. They removed the large sludge ball that had been mimicking a kidney stone on scans.