Green’s Dictionary of Slang

trac n.

[abbr. SE intractable]

1. (Aus.) a prisoner who refuses to accept the rules.

[Aus] ‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xli 4/4: trac: Intractible [sic] prisoner.
[Aus]J. Alard He who Shoots Last Preface: The Tracs (long term bad boys) whose treatment is diabolical [...] These tough boys (the Tracs) are stripped, booted and bashed.
[Aus]K. Gilbert Living Black 237: They’re a bit rough on the, what do you call the other prisoners? The tracs, yeah, the tracs [...] They’re used to treating the tracs with the rough stuff and it rubs off on to the other prisoners so they get it rough.
[Aus]B. Matthews Intractable [ebook] [I]n the hope that it would rehabilitate the ‘tracs’ from committing further breaches of prison discipline.

2. as tracs, the intractables block or maximum security section of a prison.

[Aus]B. Matthews Intractable [ebook] I began to lose all concept of time inside Grafton tracs.