Plain English Meaning
Any machine designed to fly, whether powered or unpowered, lighter-than-air or heavier-than-air.
Full Definition
A device that is used, or intended to be used, for flight in the air. This includes airplanes, helicopters, gliders, balloons, airships, gyroplanes, and powered-lift vehicles.
Context Anchor
Seen throughout FAA handbooks, regulations, checklists, and instructor explanations whenever the meaning applies broadly to flying machines rather than to one specific type.
Derivation
From 'air' plus 'craft' (an old English word meaning a vessel or vehicle, as in 'watercraft'). The word was coined in the late 1800s to cover any vessel built for travel through the air.
Why Pilots Care
The word 'aircraft' is a legal in the regulations. Rules that apply to 'aircraft' apply to airplanes, helicopters, balloons, and gliders alike, so pilots need to recognize when a regulation is talking about all flying machines versus a specific type.