Plain English Meaning
It is one of the standard 'leg types' used to code instrument procedures. The aircraft starts at a named point, flies a set heading or course outbound, and the leg ends when the aircraft is a specific distance from a particular DME station.
Full Definition
An ARINC 424 path and terminator leg type in which the aircraft flies a specified track outbound from a defined fix and ends the leg upon reaching a specified DME distance from a referenced DME station. The leg is defined by three elements: a starting fix, a track (course) to fly, and a terminating DME range from a named DME facility.
Context Anchor
Seen in RNAV and instrument , especially when describing how a published procedure leg begins and what ends it.