Plain English Meaning
Time you can legally write in your logbook because you were either flying the aircraft, being trained in it, or filling a required pilot seat. It's the kind of flight time that counts toward your licenses, ratings, and currency.
Full Definition
Flight time during which a person serves as a required pilot, receives training from an authorized instructor, or acts as pilot in command on a flight where more than one pilot is required by aircraft type or the operation being conducted. Pilot time, when properly logged, can be used to meet the requirements for a certificate, rating, or recent flight experience under 14 CFR Part 61.
Context Anchor
You will see this term when logging training, checking experience requirements, or applying for a certificate, rating, or endorsement.