Definition
A unit of apparent power in an electrical circuit, equal to the product of voltage (volts) and current (amperes), without regard to the phase relationship between them. In direct-current circuits, volt-amps and watts are equal; in alternating-current circuits, volt-amps represent the total power supplied, which may be greater than the actual working power (watts) because some current and voltage are out of phase.
Plain English
A way of measuring how much electrical power a circuit is supplying, found by multiplying volts by amps. In simple DC systems it's the same as watts, but in AC systems it can be larger than the actual usable power.
Context Anchor
Seen in aircraft electrical-system discussions, especially when rating equipment such as generators, alternators, transformers, inverters, and electrical loads.
Derivation
A compound of the two units being multiplied: 'volt' (named after Alessandro Volta) and 'amp' (short for ampere, named after André-Marie Ampère). The name literally tells you the math: volts times amps.
Why Pilots Care
Aircraft electrical components are rated in volt-amps so pilots and technicians know the actual load capacity available without overloading the system.
Intuition Check
Do not assume a volt-amp is always the same as a watt. In some circuits they match, but in many alternating-current circuits a volt-amp describes the load the source must carry, while watts describe the power actually used.
Example Sentence 1
The aircraft's static inverter is rated at 250 volt-amps, which sets the maximum AC load it can supply.
Example Sentence 2
Before adding new avionics, the mechanic checked that the alternator could handle the extra volt-amp load.