Plain English Meaning

Cockpit units that figure out where the aircraft is by listening to navigation satellites overhead. They give the pilot position, speed, and time, and on certified units they also provide approach guidance and route navigation.

Full Definition

Airborne avionics units that determine the aircraft's position, altitude, ground speed, and time by receiving signals from a constellation of navigation satellites. GPS refers specifically to the U.S. satellite system, while GNSS is the broader term covering GPS together with other satellite systems such as GLONASS (Russia), (Europe), and BeiDou (China). In operations, only receivers certified to the appropriate TSO may be used for navigation, approach guidance, and required position reporting.