masquerading

from The Collaborative International Dictionary of English v.0.48

Masquerade \Mas`quer*ade"\, v. i. [imp. & p. p. {Masqueraded};
   p. pr. & vb. n. {Masquerading}.]
   [1913 Webster]
   1. To assemble in masks; to take part in a masquerade.
      [1913 Webster]

   2. To frolic or disport in disquise; to make a pretentious
      show of being what one is not.
      [1913 Webster]

            A freak took an ass in the head, and he goes into
            the woods, masquerading up and down in a lion's
            skin.                                 --L'Estrange.
      [1913 Webster]

from The Free On-line Dictionary of Computing (8 July 2008)

masquerading

   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.

   (1998-03-03)