Green’s Dictionary of Slang

1. (Aus., also cronck, kronk) a criminal.

1889		Dead Bird (Sydney) 19 Oct. 6/1: A professional cronk, while doing a spin on the Marrickville tracks, struck up against a post and scratched his yellow hide.
1894		Truth (Sydney) 22 July 6/1: At such ‘cronks’ a word of warning is now levelled [...] ‘satisfactory explanation’ will not succeed in hiding from Truth [...] howling frauds and barefaced swindles.
1900		Sydney Sportsman (Surry Hills, NSW) 3 Oct. 1/1: The crooks, cronks and crawthumpers that are always gunning on the game.

2. (Aus./US campus) something of poor quality.

1890		Dead Bird (Sydney) 18 Jan. 7/4: Doyle [...] was supposed to be a ‘cronk’ in the Botany, and yet he got within six inches of the winner.
1997–2001		Online Sl. Dict. 🌐 cronk n 1. something of poor quality; PIECE OF CRAP. (‘That car is a cronk.’).

3. (Aus.) a criminal or duplicitous action.

1900

Sydney Sportsman (Surry Hills, NSW) 31 Oct. 1/3: Every joker that works off a cronk [...] in connection with racing appears to think The Sportsman has a down on him.

4. (US Und.) a bad cheque.

1909		Sun. Times (Perth) 12 Dec. 1/5: Papered over with cronks and stumers that the callous banks refuse.
1935		A.J. Pollock Und. Speaks 27/2: Cronck, a counterfeit race track mutual ticket [...] Cronk, a fraudulent check.

5. an unattractive woman.

1997–2001

Online Sl. Dict. 🌐 cronk n [...] 2. an unattractive female.