In article <5k7cn6$...@hermes.achilles.net>,

You're right (or at least not wrong).

All concepts of "force" are made up to describe phenomena.  If
we work in a nonrotating coordinate system there is no real
need for the concept of centrifugal force.  If we work in a
rotating coordinate system and still want F = ma to apply in
a simple-minded manner, we need the concept of centrifugal
force.  Now, you could justly say that expecting F = ma to hold
in a rotating coordinate system is a dumb idea.  However, we can
get F = ma to hold in a rotating coordinate system if we make
up two forces: the "centrifugal force" and the "Coriolis force".

One sometimes calls a force that's an artifact of a funny choice of
coordinate system a "ficitious force".  The "centrifugal force" and
the "Coriolis force" are two famous examples.  Another is gravity, but
that's a more complicated story, which one finds under General
Relativity rather than Classical Mechanics.

Both.  Webster's dictionary gives definitions but detailed
explanations.  For example, I bet it fails to note that gravity
is not really a force, but merely the curvature of spacetime.  
You might check to see what it says under "aether" or "phlogiston".

But wait!  The 1913 edition of Webster's Dictionary *does* point out
that "phlogiston" is discredited:

Phlogiston, n. [NL., fr. Gr. burnt, set on fire, fr. to set on fire,
to burn, fr. , , a flame, blaze.  See Phlox.] (Old Chem.) The hypothetical
principle of fire, or inflammability, regarded by Stahl as a chemical element.
This was supposed to be united with combustible (phlogisticated) bodies and
to be separated from incombustible (dephlogisticated) bodies, the phenomena
of flame and burning being the escape of phlogiston. Soot and sulphur were
regarded as nearly pure phlogiston. The essential principle of this theory
was, that combustion was a decomposition rather than the union and
combination which it has since been shown to be. <-- this theory is now
discredited and superseded by the theory of chemical reaction between
oxidizable substances and oxidants as an explanation of combustion -->

Wow, that *is* a pretty detailed explanation!  (I hadn't known that
soot and sulphur were regarded as nearly pure phlogiston!)  Somehow
I think more recent editions would give fewer details, as part of
the general dumbing-down (or more precisely postliterate) phase we
find ourselves in, but I don't have any newer editions available.

So, let's look up "centrifugal" in the 1913 edition...

Centrifugal force (Mech.), a force whose direction is from a center.
When a body moves in a circle with uniform velocity, a force must
act on the body to keep it in the circle without change of velocity. The
direction of this force is towards the center of the circle. If this
force is applied by means of a string to the body, the string will be
in a state of tension. To a person holding the other end of the string,
this tension will appear to be directed toward the body as if the body
had a tendency to move away from the center of the circle which it is
describing. Hence this latter force is often called centrifugal force.
The force which really acts on the body being directed towards the center
of the circle is called centripetal force, and in some popular treatises
the centripetal and centrifugal forces are described as opposing and
balancing each other. But they are merely the different aspects of the
same stress.

Whoa!  So back then, they *did* explain centrifugal force more
carefully!   Okay, so clearly your problem is that you're using a
crappy new edition instead of one of the good old ones.  In the
future, unless you are looking for new words, you should probably use
the 1913 edition, available at:

http://humanities.uchicago.edu/forms_unrest/webster.form.html