VMC

VMC - Visual Meterorological Conditions. See VFR, above.
Vnav - vertical navigation.
Volmet - continuous recorded broadcasts of weather conditions at selected airfields.

VMC. See visual meteorological conditions.
VOR. See very-high frequency omnidirectional range.

VMC
Visual Meteo Conditions ("good" weather for VFR or IFR)
VMO
maximum operating limit speed.

VMC-
(See VISUAL METEOROLOGICAL CONDITIONS.)
VOICE SWITCHING AND CONTROL SYSTEM- The VSCS is a computer controlled switching system that provides air traffic controllers with all voice circuits (air to ground and ground to ground) necessary for air ...

VMC
Visual Meteorological Conditions - Weather that offers enough visibility so that air crews can navigate and avoid other aircraft by looking outside cockpit window.

The VMC number in the Pilot's Operating Handbook is determined according to the FAR 23.149 definition. This airspeed is marked with a red radial line on the airspeed indicator, and is sometimes called the FAR 23.149 red-radial-line airspeed.15 ...

Instrument-rated pilots may control the aircraft solely by reference to instruments, but if they are flying in VMC, they are expected to look out the window to avoid other aircraft.

Instrument Meteorological Conditions (IMC) - Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling less than the minimums for visual meteorological conditions (VMC).

Regarding the other question about IMC or VMC, if you can't control the airplane by outside references then you should tell the controller that you're in IMC.

In United States aviation VFR-on-top is defined as ATC authorization for an aircraft operating under Instrument Flight Rules (IFR) to do so in Visual Meterological Conditions (VMC) at any appropriate Visual Flight Rules (VFR) altitude.

Visual Meteorological Conditions (VMC) - Weather conditions expressed in terms of visibility, distance from cloud, and cloud ceiling equal to or greater than those specified in Federal Aviation Regulations Part 91.

Rules that govern the procedures for conducting flight under visual conditions (VMC). The term is also used in the United States to indicate weather conditions that are equal to or greater than minimum VFR requirements.

Visual Meteorological Conditions (VMC)
Weather good enough for VFR flight. Pilots often say VFR when they mean VMC.
Unicom ...

IMC - instrument meteorological conditions: weather below VMC minima, see below. Also associated rating used in conjunction with UK PPL.
INCERFA - uncertainty phase of search-and-rescue procedure.

Visual Meteorological Conditions (VMC)
Visual Meteorological Conditions (VMC) (UK)
Vital Point ...

Visual Meteorological Conditions (VMC): Weather conditions that permit aircraft to be operated in accordance with visual flight rules.
VOR/DME: A VOR to which a specific kind of distance measuring device has been added. (See VORTAC.) ...

through clouds, blinding rain, snow, fog, haze, cloud ceilings below 1000ft AGL (above ground level), or a prevailing visibility of less then 3 statue miles. The local controlling facility along with will determine whether conditions are IMC or VMC ...

See also: Flight, Aircraft, Pilot, VFR, Speed