BNC
A connector for coaxial cable such as that used for some video connections and RG58 "cheapernet" connections. A BNC connector has a bayonet-type shell with two small knobs on the female connector which lock into spiral slots in the male connector when it is twisted on.
Different sources expand BNC as Bayonet Navy Connector, British Naval Connector, Bayonet Neill Concelman, or Bayonet Nut Connection.