Plain English Meaning
A paper from an FAA-approved doctor saying you are healthy enough to fly. The class of medical you hold determines what kind of flying you are allowed to do, and it expires after a set time.
Full Definition
An official document issued by an FAA-designated Aviation Medical Examiner certifying that a pilot meets the physical and mental health standards required to exercise the privileges of a particular class of pilot certificate. Medical certificates are issued in three classes (first, second, and third), each tied to specific flight activities and each with its own validity period.
Context Anchor
You will encounter this term when learning what documents a pilot must have before acting as the responsible pilot for a flight.