sludge 
/ˈslʌʤ/ noun
/ˈslʌʤ/ noun [noncount] 1 : thick, soft, wet mud 2 : a soft, thick material that is produced in various industrial processes (such as in the treatment of sewage) 3 : a thick material that can form in the oil in an engine and cause engine problems
— sludgy /ˈslʌʤi/ adjective, sludg·i·er; sludg·i·est
▪ sludgy ground
/ˈslʌʤi/ adjective, sludg·i·er; sludg·i·est ▪ sludgy ground
