Until it was added into Article 100, the term was defined in the following fine print note in the 1999 NEC.

Quote
410-1 FPN: The international term for a lighting fixture is luminaire and is defined as a complete lighting unit consisting of a lamp or lamps together with the parts designed to distribute the light, to position and protect the lamps, and to connect the lamps to the power supply.


Joe Tedesco, NEC Consultant