Meaning of SLUDGE in English
/ slʌdʒ; NAmE / noun [ U ]
thick, soft, wet mud or a substance that looks like it
SYN slime :
There was some sludge at the bottom of the tank.
industrial or human waste that has been treated :
the use of sewage sludge as a fertilizer on farm land
early 17th cent.: of uncertain origin; compare with slush .
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005