A pump in a basement floor pit that ejects collecting groundwater away from the foundation. In the Chesapeake region's clay soils it's often the only thing standing between a summer storm and a flooded basement.
Plumbing terminology in MD, DC, and Northern Virginia maps to older supply lines, basement sump pumps, water pressure regulation, and the licensing (MD PLB & GFC, VA, DC) that real plumbing work requires.