1. Any thick, viscous matter
   "The mechanic's hands were covered in engine sludge";
   - slime, goo [informal], goop [N. Amer, informal], gook [informal], guck [N. Amer, informal], gunk [informal], muck, ooze, gloop [Brit, Cdn, informal]
    
2. The precipitate produced by sewage treatment
   "The treatment plant had to dispose of tons of sludge"

Derived forms: sludges

Type of: matter, precipitate

Encyclopedia: Sludge