A foul drainage system is an underground network of pipes, drains, and gullies that collects and disposes of wastewater and sewage. However, there are several different ways to refer to this system, each with its own unique connotations and nuances. Some synonyms include sewerage system, sanitary sewer system, waste disposal system, and sewage network. Sewerage system tends to be the most common and neutral term, while sanitary sewer system emphasizes the hygienic aspects of the system. Waste disposal system and sewage network highlight the environmental impact of the system and the importance of proper management. Ultimately, the term chosen will depend on the context and audience.