Green’s Dictionary of Slang

Broadway n.

(US prison) the ground floor of a prison; it offers more space (sometimes used for overflow housing) than the upper tiers of landings outside the cells; cite 2015 refers to sollitary confinement cells .

[US]Other Side of the Wall: Prisoner’s Dict. July 🌐 Broadway: The first floor of some tiers. A wide area where inmates come and go — and occasionally may be housed if the prison is particularly crowded.
[SA]Mail & Guardian (Johannesburg) 3 Sept. 🌐 Whe he had been placed in a cell in Mangauring’s notorious ‘Broadway’ isolation section remains uncertain.

Proper name in slang uses

In compounds

Broadway battleship (n.)

(orig. US black) a New York City streetcar.

(ref. to 1913) W.D. Middleton Time of Trolley 123: New York Railways’ experimental ‘Broadway Battleship’ double-decker of 1913 was developed from the company's stepless car design.
[US] (ref. to 1915) I.L. Allen City in Sl. (1995) 88: About 1915 the hobble-skirt streetcars used in New York were called Broadway battleships.
Broadway hello (n.)

(US Und.) a friendly greeting that prefaces a homicidal attack.

[US]A.J. Pollock Und. Speaks 14/1: Broadway hello, of apparently friendly meeting and after exchange of a few words the victim is stabbed.
Broadway Joe (n.) (also Broadway boy, ...Sam, ...swell) [Broadway, New York City’s entertainment centre + joe n.1 (1b)/the proper names/swell n.1 (1)]

(US) a well-dressed idler, living off his wits and, when possible, gullible women.

[UK]Sl. Dict. 98: Broadway Swell a New York term for a great dandy, Broadway being the principal promenade in the ‘Empire City.’.
[[US]Arizona Republican (Phoenix, AZ) 29 Aug. 5/4: Majestic Theatre — To-night [...] Joe Egan ‘Broadway Boy. All new songs].
[US]Kerouac On the Road (The Orig. Scroll) (2007) 188: Hollywood Sams stood in front of swank restaurants arguing exactly the same way Broadway Sams argue at Jacob’s Beach New York.
[US] Wentworth & Flexner DAS 63/2: Broadway boy A loud, garishly dressed, small-time gambler or ladies’ man.
[US]R. Price Ladies’ Man (1985) 225: I wasn’t Broadway Joe, but I possessed a modicum of hipness nonetheless.