Green’s Dictionary of Slang

1. to talk loudly and aggressively; also as n., and adj.; thus broadcaster n., broadcasting n.

1926		Maines & Grant Wise-crack Dict. 5/1: Broadcaster – Repeater of everything he hears.
1928		R. Carr Rampant Age 227: Happy’s giving that all-night stag radio party that he had to postpone [...] It’s time to do a little broadcasting about it.
1935		(con. late 1920s) L. Hughes Little Ham Act II: tiny: Gussie’s a troublemaker. Always talking. [...] lulu: Yes, she’s too broadcast.
1940		W.R. Burnett High Sierra in Four Novels (1984) 432: Hi kid. It’s the old man broadcasting.
1963		A.S. Fleischman Venetian Blonde (2006) 147: She had them tuned out, but they kept broadcasting.
1975		Bulletin (Sydney) 26 Apr. 45: So all right, we all move in and the Limp starts his broadcast and Marg pulls the manager into his office.

2. (Aus. Und.) to give evidence in court.

1936

Newcastle Sun (NSW) 27 May 7/4: S.P. Glossary [...] Broadcasting — Giving evidence.