Green’s Dictionary of Slang

1. a mistress one visits only at the weekend.

1984

Partridge DSUE (8th edn) 1315/2: from 1880s.

2. a weekend cottage.

1921		Newcastle Sun (NSW) 25 Aug. 6/2: The week-ender, which stands in an isolated position on the water-frontage of a large paddock, has not been used by the owner for a long time, but it is thought that it was broken into during the past fortnight.
1941		Baker Popular Dict. Aus. Sl. 81: Weekender, a week-end holiday cottage or shack.
1985		R.G. Barrett You Wouldn’t Be Dead for Quids (1989) 42: I got a weekender up there, there’s no one in it at the moment.
1999		G. Seal Lingo 98: We still take our leisure pretty seriously [...] enjoying the ‘weekender’ or beach shack as much as possible.
2000		R.G. Barrett Leaving Bondi (2013) [ebook] Warren was down the south coast at Ulladulla, in a weekender with a blonde actress.
2019		C. Hammer Silver [ebook] ‘The wealthy buy weekenders but they don’t live in them’.

3. (drugs) someone who is not a serious drug taker, thus not addicted.

1955		H. Braddy ‘Narcotic Argot Along the Mexican Border’ in AS XXX:2 89: The metonym weekender for an occasional user of drugs.
1964		Larner & Tefferteller Addict in the Street (1966) 82: All of us became addicts – only one didn’t. He was what we considered a weekender.
1989		(con. 1982–6) T. Williams Cocaine Kids (1990) 98: Both the regulars and the weekenders seek the club’s special ambience.

4. a suitcase suitable for packing those items needed for a weekend’s trip or holiday.

1961		Harper’s Bazaar June 24/2: A capacious week-ender in pale coffee-bean hide [OED].
1996		Penguin Bk of More Aus. Jokes 456: At Nar Nar Goon, they grow very, very big pumpkins. So big that they carve them out and use them for weekenders.

5. (US prison) a person who serves their prison sentence at weekends only.

1975

J. Carr Bad (1995) 101: The ‘weekenders,’ dudes busted on a petty beef, with steady jobs and families, who served their time on weekends.

6. (N.Z.) a temporary resident, rather than a permanent one.

2003

McGill Reed Dict. of N.Z. Sl. 227: weekender Casual, as compared to permanent, resident.