three-out, adv. — Green’s Dictionary of Slang

three-out adv.

(Aus. prison) three prisoners sharing a cell.

1984

B. Ellem Doing Time app. C 244: think they believe that if you’re one out by yourself all the time, you’re a psychopath. If you’re two out then you’ve got to be fucking one another. If you’re three out you’re a gang of louts.