1. <networking> "NAT" (Linux kernel name).
2. <messaging> Hiding the names of internal e-mail client and gateway machines from the outside world by rewriting the "From" address and other headers as the message leaves the organisation.
This is good practise because external users do not need to know about internal changes in message routing. The external mail gateway needs to know how to route incoming replies back to the original sender.
Try this search on Wikipedia, OneLook, Google
Nearby terms: Mask Read-Only Memory « MASM « MasPar Unity « masquerading » Massachusetts Institute of Technology » massage » Massey Hope