front end

from WordNet (r) 3.0 (2006)

front end
    n 1: the side that is forward or prominent [syn: {front}, {front
         end}, {forepart}] [ant: {back end}, {backside}, {rear}]

from Jargon File (4.4.4, 14 Aug 2003)

front end
 n.

   1. An intermediary computer that does set-up and filtering for another
   (usually more powerful but less friendly) machine (a back end).

   2. What you're talking to when you have a conversation with someone
   who is making replies without paying attention. "Look at the dancing
   elephants!" "Uh-huh." "Do you know what I just said?" "Sorry, you were
   talking to the front end."

   3. Software that provides an interface to another program `behind' it,
   which may not be as user-friendly. Probably from analogy with hardware
   front-ends (see sense 1) that interfaced with mainframes.

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

front end

   1. An intermediary computer that does set-up and filtering for
   another (usually more powerful but less friendly) machine (a
   "back end").

   2. Software that provides an interface to another program
   "behind" it, which may not be as {user-friendly}.  Probably
   from analogy with hardware front-ends that interfaced with
   {mainframes}.

   [{Jargon File}]