Plain English Meaning
It is one of the entry routes printed on an arrival chart, named after the Ephrata navigation point. Pilots arriving from that area follow this route to feed onto the main arrival into the destination airport.
Full Definition
A named transition route on a Standard Terminal Arrival Route (STAR) that begins at or near the Ephrata VOR (EPH) in Washington State and connects en route traffic to the common arrival path of the STAR. Like all STAR transitions, it specifies the fixes, courses, altitudes, and speeds aircraft must follow when joining the arrival from that direction.