Green’s Dictionary of Slang

1. one’s fancy or favourite.

1882		Sydney Sl. Dict. (2 edn) 3: Dart - Object of attraction, or enticing thing or event, or a set purpose.
1898		W.T. Goodge ‘Australia’s Pride’ in Bulletin 3 Sept. 32: But bushmen’s games are not the games / That Sydney spielers play; / A country smarty’s ‘just their dart,’ / The city sharpers say.
1902		‘Dads Wayback’ in Sun. Times (Sydney) 29 June 12/2: ‘[D]ressin’ up and pawin’ men about is about ther dart o’ most women’.

2. an illicit activity, a ‘racket’.

1888		‘Rolf Boldrewood’ Robbery Under Arms (1922) 29: The great dart is to keep the young stock away from their mothers until they forget one another, and then most of the danger is past.
1907		Brisbane Courier 29 May 6/3: ‘Lurk’ is distinctly an improvement on ‘dart,’ for it suggests concealment and a plan.

3. a plan, an aim, a scheme.

1882		in Sydney Sl. Dict.
1890		‘Rolf Boldrewood’ Colonial Reformer I 78: My dart was to get to this place.
c.1905		J. Furphy Rigby’s Romance (1921) 🌐 Ch. viii: All in favour o’ this dart will please signify the same in the usual manner.
1906		E. Dyson Fact’ry ’Ands 100: ’Twas now me dart t’ get inter ther ’ands iv ther John, ’n’ that was an easy one.
1911		L. Stone Jonah 60: Your dart is ter be king of the push.
1918		K.F. Purdon Dinny on the Doorstep 58: I’d say, the theatre would be yer best dart.
1924		C.J. Dennis ‘’Ave a ’Eart!’ in Rose of Spadgers 74: The man’s ’arf dead a’ready! Wot’s yer dart?
1947		N. Lindsay Halfway to Anywhere 79: Trucking’s my dart too.

4. a try, a ‘go’.

1881		Bulletin (Sydney) 12 Feb. 8/1: ‘Courtship and Marriage’ was Lotti’s last ‘dart.’.
1953		K. Tennant Joyful Condemned 39: Might as well have a dart at it now we’ve got the car.

5. a good idea.

1905		Bulletin (Sydney) 13 July 14/3: ‘Where’s Guam?’ I asked. ‘Anywhar and nowhar,’ he said. ‘But I don’t mind telling you it means London by circumbendibus’ ‘Just my dart,’ said I, and booked at the agents.
1914		Joyce ‘Counterparts’ Dubliners (1956) 90: Suddenly, as he was fingering his watch chain, he thought of Terry Kelly’s pawn-office in Fleet Street. That was the dart!
1979		H. Leonard A Life (1981) Act I: That’s the dart: nothin’ like an even number.