Plain English Meaning

A short stretch of an airway where the normal minimum altitude is high enough for terrain and obstacles, but the navigation signal from the ground stations may fade out. The chart tells you where the gap is and how long it is.

Full Definition

A published segment of an airway where the Minimum Enroute Altitude (MEA) does not provide guaranteed navigation signal coverage from the ground-based navigation aids defining that route. The gap is charted, its length is specified, and pilots may legally fly through it provided they can maintain course by other approved means.