Definition
The weight of an aircraft as delivered from the manufacturer, including the airframe, engines, all permanently installed equipment, unusable fuel, and full operating fluids (such as engine oil and hydraulic fluid). It does not include optional equipment added by the owner, usable fuel, passengers, or baggage.
Plain English
The factory weight of the airplane with everything that came on it from the manufacturer, plus the fluids needed to run it, but with no usable fuel and nothing loaded into it.
Context Anchor
Seen in weight-and-balance discussions when separating the airplane’s built-in weight from the load the pilot adds for a flight.
Derivation
Standard' here means 'as built to the manufacturer's standard configuration.' 'Empty' means without the variable load (fuel, people, baggage). Together, the phrase points to the baseline weight of a stock airplane before anything is added or loaded.
Why Pilots Care
This baseline weight is required to accurately determine takeoff weight, center of gravity, and performance limits for every flight.
Intuition Check
“Empty” does not mean the airplane contains nothing. In this term, it means no people, baggage, or usable fuel, while certain installed items and required fluids are still counted.
Example Sentence 1
The standard empty weight listed in the manufacturer's specifications was the starting point for calculating the airplane's licensed empty weight after the new avionics were installed.
Example Sentence 2
Adding the weight of the new radios to the standard empty weight gave the basic empty weight for the airplane.