Green’s Dictionary of Slang

1. (UK Und., a thief or burglar who operates at night; Irish) usu. a cattle thief.

1883		J. Greenwood Tag, Rag & Co. 96: The road on either side is bounded with a low wall [...] that would delight the heart of an Irish ‘Moonlighter’.
1890		Hants Advertiser 23 July 4/2: The two masked and mysterious muscians who made their appearance [...] look like the pictures we see of moonlighters.
1914		Sport (Adelaide) 3 July 4/7: ‘Sport’ wishes to inform Bert R. the Moonlighter, that Kadina chaps come to Wallaroo fishing — not to see if they can do moonlighting .
1915		G. Fitzmaurice Moonlighter in Five Plays (1917) 83: You dare go against the rules while I’m the Captain of the moonlighters!
1924		G. Henderson Keys to Crookdom 411: Moonlighter. One who steals at night.
1934		in WNID 1054: moonlighter ‘One who follows an occupation or pastime by night’.
1939		Howsley Argot: Dict. of Und. Sl.
1949		Monteleone Criminal Sl. (rev. edn).

2. one who escapes paying the rent by leaving a house late at night.

1905		J. Wright EDD.
1964		Sun. Mail (Brisbane) 15 Nov. 12: Brisbane flat owners...estimate that moonlighters — tenants who slip away overnight without paying the rent — are costing them £100,000 a year .

3. a smuggler of illicitly distilled liquor.

1887		Catholic World XLIV 706: [...] the male sex as found in the land of hidden whiskey-stills and moonlighters.
1973		H. Robertson Grass Roots 249: The same recipe that the Bienfait moonlighters used and disguised as imported whiskey by false labels.
2003		K. Bender Ark of the Rainbow 62: If there was ever a man born to the task, it was Reggie, a natural moonlighter [...] he came back with two beers for each of us.

4. one who takes a second job, undeclared for tax purposes.

1957		Chicago Sun. Trib. 8 July 14/1: The moonlighter [...] is a guy who holds two jobs.
1968		K. Brasselle Cannibals 143: I had a strange feeling ‘William S. DeMarco’ might be a moonlighter.
1968		‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 48: moonlighter – Doing extra jobs on the side.

5. (US teen) one who betrays their regular partner.

1968

‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 48: moonlighter – [...] cheating on your chick.

6. (US black) a prostitute.

1983		R. Klein Jailhouse Jargon and Street Sl. [unpub. ms.].
1989		J. Morton Lowspeak.