Plain English Meaning

It means the aircraft can figure out where it is accurately enough for the procedure by using distances from two ground DME stations at the same time, instead of using GPS.

Full Definition

A Required Navigation Performance (RNP) capability in which the aircraft determines its position by simultaneously measuring distances from two or more ground-based DME stations, and meets a specified accuracy standard for that segment of flight without relying on GPS or other navigation sources.

Context Anchor

Seen in instrument approach chart notes and equipment requirements, especially where a procedure may allow or restrict navigation based on DME/DME instead of GPS.

Derivation

DME comes from ',' a that measures from the aircraft to a ground . RNP comes from 'Required Navigation Performance,' which sets a minimum accuracy the navigation system must meet. Combining them describes a navigation method that uses two DME signals to satisfy that accuracy requirement.