Plain English Meaning
The first time a student pilot flies an aircraft on their own, with no instructor in the cockpit. The instructor decides the student is ready, signs them off, and stays on the ground while the student takes off, flies a short pattern, and lands.
Full Definition
The first occasion on which a student pilot flies an aircraft alone, without an instructor or any other person on board, after the instructor has endorsed the student's logbook authorizing solo flight. It is a major milestone in primary flight training and typically consists of a short flight in the traffic pattern, including takeoff, circuit, and landing.
Context Anchor
Seen in flight training, student pilot progress records, and instructor discussions when a student is ready to fly without the instructor in the aircraft.