Plain English Meaning
It is the spot on a route where you stop tuning and tracking the VOR station behind you and start tuning and tracking the VOR station ahead of you.
Full Definition
A point along the centerline of a Federal airway, jet route, or other published route segment where a pilot navigating by VOR is expected to switch navigation reception from the station behind the aircraft to the station ahead. The COP is normally located at the midpoint between the two facilities, but it may be published at a different location when terrain, signal coverage, or route geometry require the changeover to occur somewhere other than the midpoint.