NIC can refer to three things.
#1. Network Information Center. Refers to any office that handles information on a network. For example, InterNIC itself (
www.internic.net). Nominet is the "NIC" for .co.uk domains. If you went to
www.nic.ch, you would arrive at "Switch", the NIC for .ch and .li domains.
#2. Network Interface Card. The card in your computer that lets you connect to a network (or the Internet via your cable modem).
#3. Shortened version of "NIC Handle", previously described. This is the least frequent usage I've encountered. It also leads to confusion as a NIC Handle, isn't really a NIC.
Even my favorite glossary:
www.whatis.com doesn't contain the first definition of NIC. Ug. But...
www.netlingo.com/inframes.cfm
~ W|Z