Green’s Dictionary of Slang

1. (Aus.) large.

1857		Bell’s Life in Victoria (Melbourne) 23 May 2/4: A booming three-railer was the first impediment to following him.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.

2. grand.

1884

(con. c.1840) ‘Mark Twain’ Huckleberry Finn 135: We can just have booming times — they don’t have no school now.

3. successful, flourishing.

1952		W.R. Burnett Little Men, Big World 144: Things are booming, as you know.
1964		E. Wilson Earl Wilson’s New York 4: Toots Shor’s is probably the boomingest celebrity trap of all.

4. (US black) good-looking.

1994

G. Smitherman Black Talk.

5. (US campus) excellent, worthy of approval.

1992		R.C. Cruz Straight Outta Compton 114: ‘What is that?’ Clive asked. ‘A boomin’ system,’ said somebody.
1996		Eble Sl. and Sociability 56: The following functionally synonymous slang terms from two school years, 1990–91 and 1991–92, all mean ‘excellent, worthy of approval’: awesome, bad, bitching, booming.
1996		UGK ‘Fuck My Car’ 🎵 Oh yeah these hoes think they cute in skin-tight catsuits / ssumin that they body’s too boomin to dispute.