Green’s Dictionary of Slang

blow off n.1

[blow v.1 ]

1. (US) an emotional outburst; a sudden fight or argument; a sensational piece of news.

O.W. Holmes Jr. letter 29 Mar. in Howe Justice O.W. Holmes (1957) I 150: I had my blowoff in one of my last [i.e. letters] and now let bygones be bygones.
[UK]S.M. Fergusson in ‘House’ on Sport I 174: A blow-off in this wise [i.e. swearing at golf] does one good now and then [OED].
[US]D. Runyon ‘Fat Fallon’ in From First to Last (1954) 29: He was in barracks in Manila, before the gugu blow-off.
[US]P. Kyne Cappy Ricks 303: I planned to be away from the office when the blow-off came, and you were to bear the brunt of Matt’s fury and despair.
[US]E.S. Gardner Case of the Sulky Girl (1941) 188: Save a big slice of the front page for a blow-off.
[US]J.M. Cain Postman Always Rings Twice (1985) 147: What we had the big blow-off over was the beer license.
[US]Howsley Argot: Dict. of Und. Sl.
[US]W. Guthrie Bound for Glory (1969) 353: You’re not going to hurt anybody, Mister Blowoff!
[US]I. Shulman Cry Tough! 60: He knew his father was steaming himself up for a big blow off.
[UK]I, Mobster 72: It was clear that sooner or later something would have to give and there would be a blowoff.

2. a party, a celebration.

[US]Nat. Police Gaz. (NY) 2 Oct. 14/2: Muirie Is going to give the boys a big blow off when the New Yorks win the championship in 1901.
[US]C.L. Cullen Tales of the Ex-Tanks 91: I had it all plotted out [...] to give my old boyhood home a blow-off for a week or so.
[US]Ade Knocking the Neighbors 6: The Blow-Off came on the Trip to the City. That was the Big Entertainment.
[US]G. Bronson-Howard God’s Man 211: A blow-off one girl’s giving who’s going across the big ditch – Europe.

3. a braggart.

[US]Chronicle-Telegram (Elyria, OH) 29 Sept. 5/5: ‘Livin’ on his jawbone’ is an expressive way of describing a blow-off.

4. (N.Z.) boasting.

[NZ] McGill Reed Dict. of N.Z. Sl.