Plain English Meaning
The companies that make the electronic boxes and screens in the cockpit, and the software that runs them.
Full Definition
Companies that design and produce the electronic equipment installed in aircraft, including navigation receivers, flight management systems, autopilots, communication radios, and the navigation databases that drive them. In the context of airborne navigation databases, avionics manufacturers are the entities that build the cockpit equipment which loads, stores, and uses the navigation data supplied by data providers.
Context Anchor
Seen when reading about airborne navigation databases, database updates, and whether a database is compatible with the equipment installed in the aircraft.
Derivation
"Avionics" is a blend of "aviation" and "electronics," coined in the 1940s as aircraft began carrying more electronic . So an avionics manufacturer is simply a maker of aviation electronics.