Green’s Dictionary of Slang

1. to kill with a firearm, to shoot dead.

1871		W. Still Underground Railroad 433: Jim had a [...] pistol and counted on ‘blowing a man down if anyone touched’ him.
1926		Odum & Johnson Negro Workaday Songs 70: O Lawd, / Shot my pistol / In the heart of town. / Lawd, the big chief hollered, / ‘Doncha blow me down’.
1935		A.J. Pollock Und. Speaks.
1958		Hughes & Bontemps Book of Negro Folklore 354: Late las’ night I was a-makin’ my rounds, / Met my woman an’ I blowed her down, / Went on home an’ I went to bed, / Put my hand cannon right under my head.
1975		J. Wambaugh Choirboys (1976) 44: You’d like to blow em down, wouldn’t you?

2. (US Und.) to modify, to soften.

1931

‘Und. “Lingo” Brought Up-to-Date’ L.A. Times 8 Nov. K3: BLOW DOWN: To modify; to soften; to quash.

3. to defeat comprehensively, to overwhelm.

1951		C. Stoker Thicker ’n Thieves 49: [T]he district attorney and the sheriff must stand shoulder to shoulder [...] to emasculate and mitigate, to blow down and squelch any and all efforts anyone may make to interfere with the status quo.
1962		R. Houk Ballplayers Are Human 118: He’d been the hero of the ’58 series, hurling two beautiful games to blow the Braves down.
1986		D. Barker Life in Jazz 129: Reuben Reeves [...] who, on an occasion when Louis [Armstrong] played the Regal, attempted some intrigue and serious planning in order to blow Louis down.

4. (US) to quash.

1951

C. Stoker Thicker ’n Thieves 227: [I]f the district attorney is ‘interested’ in ‘blowing down the beef’ rather than in bringing malefactors to justice, his deputy will follow the boss’s line.

5. to pass at high speed.

1984

W. Murray Tip on a Dead Crab 211: Charlie’s gonna blow him down in the stretch.

6. see blow in v.²