BNC may refer to any of the following:
1. Short for Bayonet Neill-Concelman connector, a BNC connector is a type of connector used with coaxial Ethernet cable. The connector is bayonet-style, meaning that it is put in then turned and locked in position. This connector is commonly used on a Token Ring network. BNC is also referred to as the Bayonet Nut Connector or British Naval/Navy Connector although more appropriately known as the Bayonet Neill-Concelman. Below is an example of a BNC connector. In the picture two BNC cables are connecting to a BNC splitter.
2. Short for bouncer, BNC is software helps protect and hide a user by relaying their IRC or FTP traffic over a network to their computer. For example, a user may connect to a computer using psyBNC, relay traffic from that source, and connect to an IRC or FTP to hide their IP address. When this is done, the IP address would be for the computer that is running the BNC software.