roundabout, n. — Green’s Dictionary of Slang

roundabout n.

1. (UK prison) the treadmill.

1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 150: Round-about — the tread-mill recently invented for the employment of convicts in prison, is thus denominated by them. ‘About she goes,’ said when at work.
1824		Pierce Egan’s Life in London 26 Sept. 5/2: [I]t appears his Lordship, in a former part of his life, filched some ropes, for which he was taken, and put upon the ‘round-about’.
1863		Stamford Mercury 25 Dec. 5/5: The magistarate kindly treated them with 21 days at the ‘roundabout’.

2. (US) a prize-ring.

1835

N.Y. Transcript 4 Feb. 2/2–3: Walking up to the ropes, he threw his castor into the round-about.

roundabouter (n.)

(Aus.) a resident of the Australian Capital Territory.

2022

D. Andrew Aussie Sl. 10: Round-a-bouters Residents of the Australian Capital Territory.