A network topology in which all nodes are connected to a single wire or set of wires (the bus). Bus networks typically use CSMA/CD techniques to determine which node should transmit data at any given time.
Some networks are implemented as a bus, e.g. Ethernet - a one-bit bus operating at 10, 100, 1000 or 10,000 megabits per second. Originally Ethernet was a physical layer bus consisting of a wire (with terminators at each end) to which each node was attached. Switched Ethernet, while no longer physically a bus still acts as one at the logical layers.