Short for network interface card (NIC) bonding it is a term used to describe a way to increase available bandwidth. When bonded, two NICs appear to be the same physical device and they also have the same MAC address. Linux uses a special kernelmodule called bonding to allow users to bond multiple network interfaces into a single channel. NIC bonding may also be called NIC Teaming.
See “Understanding NIC Bonding with Linux” on EnterpriseNetworkingPlanet.