∙ The pipes, together with the joints, tanks, stopcocks, taps and other fixtures of a water, gas or sewage system in a house or other building. uncountable
∙ The trade or occupation of a plumber. uncountable
∙ A system of vessels or ducts in the human body, especially the genitourinary system. uncountable, informal
∙ A Murasugi sum where each disk summed along has its boundary subdivided into four segments. countable
∙ Something practical, concrete, real, down to Earth uncountable, informal