Plain English Meaning
The point on the chart where a published departure procedure stops. Once the aircraft passes it, the departure is over and the en route part of the flight begins.
Full Definition
The published fix at which a Standard Instrument Departure (SID) ends and the en route portion of the flight begins. It is the last charted waypoint of the SID, where the aircraft transitions from the departure procedure to its filed en route route or to a clearance issued by ATC.
Context Anchor
Seen on instrument departure procedures and in navigation database discussions, especially when route ends at a named waypoint or fix.