Surprisingly, a search for "instrument meteorological conditions" in Chapter
14 of the CFRs yields only 6 hits, most referring to training, the only
definition being found in part 170.3 (below). A similar search for IMC
yields only 2 hits, both in part 170.3.

FAR Part 1 Definitions:
IFR conditions means weather conditions below the minimum for flight under
visual flight rules.

FAR 170.3
Instrument flight rules (IFR) means rules governing the procedures for
conducting flight under instrument meteorological conditions (IMC)
instrument flight.
Instrument meteorological conditions (IMC) means weather conditions below
the minimums prescribed for flight under Visual Flight Rules (VFR).

To that end, what purpose does this serve?

It appears that the FAA has taken what was once a very easy to understand
concept and the phrase that clearly defined it and fubared it beyond belief.
If IMC is no longer "actual meteorological conditions requiring flight
solely by reference to instruments", why use the acronym or the term?

The next question this fubar brings to the table is what constitutes
loggable actual instrument flight?

From Assistant Chief counsel, John Cassidy -
"Section 61.51(c)(4) provides rules for the logging of instrument flight
time which may be used to meet the requirements of a certificate or rating,
or to meet the recent flight experience requirements of Part 61. That
section provides in part, that a pilot may log as instrument flight time
only that time during which he or she operates the aircraft solely by
reference to instruments, under actual (instrument meteorological conditions
(imc)) or simulated instrument flight conditions. "Simulated" instrument
conditions occur when the pilot's vision outside of the aircraft is
intentionally restricted, such as by a hood or goggles. "Actual" instrument
flight conditions occur when some outside conditions make it necessary for
the pilot to use the aircraft instruments in order to maintain adequate
control over the aircraft. Typically, these conditions involve adverse
weather conditions."

"Actual instrument conditions may occur on a moonless night over the ocean
with no discernible horizon, if use of the instruments is necessary to
maintain adequate control over the aircraft. The determination as to whether
flight by reference to instruments is necessary is somewhat subjective and
based in part on the sound judgment of the pilot. Note that, under Section
61.51(b)(3), the pilot must log the conditions of the flight. The log should
include the reasons for determining that the flight was under actual
instrument conditions in case the pilot later would be called on to prove
that the actual instrument flight time logged was legitimate."

To answer the OP, I simply fly the airplane. My normal mode of operation is
to use both outside visual references and reference to the instruments. The
degree to which I use either, depends upon the conditions at any given
moment.

Jim