Learner's definition of SLUDGE
[noncount]
2
: a soft, thick material that is produced in various industrial processes (such as in the treatment of sewage)工业污物；工业淤渣
3
: a thick material that can form in the oil in an engine and cause engine problems（发动机里的）油污
— sludgy
/ˈslʌʤi/ adjective sludgier; sludgiest