: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." See also {fepped out}. 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.
-- The AI Hackers Dictionary