A suspension of water and solid waste, transported by sewers to be disposed of or processed.
"The city's aging infrastructure struggled to handle the volume of sewage flowing through the main sewer lines during the heavy rainstorm."
In plain English: Sewage is dirty water and waste from homes that gets sent to be cleaned up so it doesn't make people sick.
"The new treatment plant was built to clean the city's sewage before it reached the river."
Usage: Sewage refers specifically to wastewater containing household solids that is carried through underground pipes for treatment. Do not confuse this term with general "waste," as it strictly denotes liquid effluent moved via a sewer system rather than solid trash left in landfills.
The word sewage comes from the noun sewer, which originally referred to a system of pipes for removing waste and providing drainage. The suffix -age was added to this term to create a general name for the liquid matter itself.