Plain English Meaning
The knobs, buttons, or softkeys the pilot uses to set up the airplane's navigation radios and choose which navigation signal the flight display follows.
Full Definition
The cockpit controls used to tune, select, and manage the navigation radios and navigation sources displayed on an electronic flight display. NAV controls let the pilot select VOR, ILS, GPS, or other navigation inputs, switch between active and standby frequencies, and choose which navigation source drives the course deviation indicator and flight director.