Definitions of Network Address Translation (NAT) on the Web:

• In computer networking, network address translation (NAT) is the process of modifying network address information in datagram packet headers while ...
  en.wikipedia.org/wiki/Network_address_translation

• An Internet standard that enables a LAN to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. ...
  www.telecombooksblog.com/telecom-glossary-n/

• This is a means of hiding the IP addresses of PCs on a home LAN from the Internet while still allowing the PCs on the LAN to access the Internet. ...
  cyberangelscorporate.com/network.aspx

• A type of network connection that lets a virtual machine use the IP address and MAC address of the host.
  wiki.novell.com/index.php/Terminology_-_Novell_Virtualization_Platform