Green’s Dictionary of Slang

moonlight v.

[to operate by SE moonlight]

1. (Aus./Irish) to steal cattle; thus moonlighting n.

[Aus]Sport (Adelaide) 3 July 4/7: Kadina chaps come to Wallaroo fishing — not to see if they can do moonlighting .
[Aus]N. Pulliam I Travelled a Lonely Land (1957) 236/1: moonlighting – riding out to hunt sheep or cattle at night.
[Ire]P.J. Flanagan Cavan and Leitrim Railway 12: Despite the forthright condemnation of the priests a ‘Captain Moonlight’ roamed the Leitrim hills and ‘moonlighting’ became a common pastime .

2. (UK Und.) to engage in criminal activity at night.

[US]Berrey & Van den Bark Amer. Thes. Sl.
[US]Monteleone Criminal Sl. (rev. edn).

3. (orig. US) to work at two jobs in order to boost one’s income. The second job is usu. night work, and the other employer may not know about it; thus more usu. as the n. moonlighting

[US]E. Tidyman Shaft 35: Cops were moonlighting as armed cab drivers.
[US]L. Kramer Faggots 116: He moonlighted, writing twice-monthly features.
[US]D. Woodrell Muscle for the Wing 73: I hear he moonlighted as a collector for a loan shark.
[US]C. Fletcher Pure Cop 109: We get a lot of medical students. They moonlight as pimps and male prostitutes.
[UK]Guardian G2 22 July 7: Must he moonlight as a columnist?
[US]K. Huff A Steady Rain I iii: He’d stay out late and tell Connie he was moonlighting.
[Scot]L. McIlvanney All the Colours 117: ‘They were over here building chapels and they did this place on the side. Moonlighting’.
[US]G. Hayward Corruption Officer [ebk] cap. 22: I moonlight on my days off doing unauthorized security at the local clothing stores.
[UK]K. Sampson Killing Pool 216: He’s moonlighting [...] for a few dollars more.

In derivatives

moonlighting (n.)

taking a second, usu. late-night, job in addition to one’s daily employment; also in fig. use, i.e. doing something other than what one should be or claims to be.

[US]Reporter 8 Aug. 11/3: He takes two or three hours off and then, refreshed by a nap and an early dinner, departs for a second job. . . . The practice is known as ‘moonlighting’.
[US]P. Rabe Murder Me for Nickels (2004) 55: Benotti’s got all non-labour [...] six men and they all do moonlighting on the side.
[US]H.S. Thompson letter 7 June in Proud Highway (1997) 383: Yours of May 18 reached me [...] forwarded via the Observer with a menacing comment about ‘moonlighting’.
[US]B. Hamper Rivethead (1992) 60: Dale was going to have to pull sixty years of moonlighting [...] to pay off his fleet of farmyard bloodsuckers.
[UK]N. Cohn Yes We have No 279: There are so many other ways to get ahead. Moonlighting; resales; the black market.
[UK]J.J. Connolly Viva La Madness 223: It was his moonlighting that brought this mess down on everybodys heads.