Plain English Meaning

Everything a student pilot does with an instructor on board, leading up to the day they are cleared to fly the aircraft by themselves for the first time.

Full Definition

The phase of flight training that occurs before a student pilot is authorized to fly an aircraft alone. During this phase, the student trains with an instructor and must demonstrate satisfactory knowledge and skill in specified maneuvers and procedures, and pass a pre-solo written test administered by the instructor, before being endorsed to fly solo.

Context Anchor

Seen in flight training syllabi, instructor signoffs, and discussions of what a student must learn before the first solo flight.

Derivation

From the Latin prefix 'pre-' meaning 'before,' combined with 'solo' from Italian, meaning 'alone.' So pre-solo literally means 'before flying alone' — which is exactly what the phase describes.