Plain English Meaning
The starting fix of an arrival procedure. It's where the published arrival 'begins' on the chart, and where you join it when flying in.
Full Definition
The first fix of a Standard Terminal Arrival Route (STAR), where the published arrival procedure begins. It is the point at which an aircraft transitions from the en route phase onto the charted STAR and begins flying the sequence of fixes, altitudes, and speeds that lead toward the destination airport.
Context Anchor
Seen on STAR charts and in instrument clearances when a published arrival route starts at a named point.