A nut with a built in washer like flange. Tee. A nut designed to be driven into wood to create a threaded hole. Square. A four sided nut. Prevailing torque lock. A non-reversible lock nut used for high temperature applications. K-Lock or Kep. A nut with an attached free-spinning external tooth lockwasher.
adjective. The definition of metropolitan is a city or something related to a city. A city and the immediate locations surrounding it is an example of a metropolitan area.
Metropolitan Statistical Area (MSA). In the United States, a central city of at least 50000 population, the country within which the city is located, and adjacent countries meeting one of several tests indicating a functional connection to the central city.