Collision
Term used to describe when one or more computers or networking devices attempt to send data at the same time to one computer, server, or other network device. When collisions are encountered, the computer, server or network device will send back a request to try sending the data again.
Network collisions can be easily determined on many network cards and other network hardware by looking for an amber or red light ellumination. Network collisions can also be detected by using software or diagnostic programs on some network hardware.
Also see: Amber, CSMA/CD, LED, Network definitions, Red