A type of connector commonly used on beer and gas lines in kegging systems, to allow lines to be reconfigured easily.  The male fitting consists of a cylinder with external threads, and a tapered end.  The female fitting consists of a flared piece that mates with the tapered end of the male fitting, with a threaded nut over it that screws onto the threads on the outside of the male fitting.   Typically, the gas/beer lines have female fittings on them, and the keg disconnects, distribution manifolds, etc. have male fittings.  Some male fittings have a plastic coated tip, and can be used without a washer; all-metal fittings should be used with a plastic washer, to ensure a gas (or beer) tight seal.