1Illumination of a room, building, etc., by sunlight; the degree or strength of this.
2 informal The practice of having a second job in addition to one's regular employment, which is undertaken during the day (rather than at night).
Originally in explicit contrast with moonlighting, although the latter is now commonly used to refer to daytime jobs as well as night work.
Mid 19th century; earliest use found in London Reader. From sunlight + -ing, in sense 2 after moonlighting.