The term 'Underground System' can be summarized as a system of pipes and tunnels that are used to transport wastewater away from buildings and other structures. The term is often associated with the word 'SEWER, ' which is a five-letter word used to describe a system of pipes and tunnels that carry wastewater away from buildings and other structures. Sewers are an important part of any underground system, as they help to keep the environment clean and safe by preventing wastewater from entering natural water sources.