Green’s Dictionary of Slang

hot air n.

1. (orig. US) nonsense, rubbish, empty chatter.

[1873		‘Mark Twain’ & C. Warner Gilded Age 399: The most airy scheme inflated in the hot air of the capital only reached in magnitude some of his lesser fancies, the by-play of his constructive imagination].
1899		Ade Fables in Sl. (1902) 126: They strolled under the Maples, and he talked what is technically known as Hot Air.
1910		‘O. Henry’ ‘The Fifth Wheel’ in Strictly Business (1915) 72: He fed me on biscuits and hot air, and then kicked me down the front steps.
1917		A.S.G. Lee letter in No Parachute (1968) 20 May 7: A lot of bally hot air, they’re just trying to put the wind up us new boys.
1927		E. Wallace Squeaker (1950) 73: Do you think that’s hot air?
1939		V. Davis Gentlemen of the Broad Arrows 72: Most of us thought that Browne was merely releasing ‘hot air’.
1946		D. Stivens Courtship of Uncle Henry 39: There was only hot air in his protests.
1947		Kerouac letter 26 Aug. in Charters I (1995) 117: Is this all a lot of hot water? Not from this point of view: that we will all die some day and it would be one hell of a joke if we all died in darkest ignorance of one another.
1957		H. Simmons Corner Boy 196: They were scared by all that newspaper hot air about teen-age gangs.
1960		J.P. Donleavy Fairy Tales of N.Y. III i: Now why don’t you two be friends and instead of wasting a lot of hot air on each other, use this room the way it’s supposed to be used.
1978		(con. 1940s) J.G. Farrell Singapore Grip 128: Geneva [...] is a city of hot air and hypocrites.
1983		(con. 1950s) D. Nobbs Second From Last in the Sack Race 301: Suddenly his ‘A’ levels were looming [...] Brave talks about exams not being valid tests of a man’s worth were so much hot air.
1999		Indep. The Information 9–15 Oct. 59: The fuss surrounding Eyes Wide Shut turned out to be hot air.
2001		‘Randy Everhard’ Tattoo of a Naked Lady 57: Hot air’s good for nothin’ but balloons.
2016		D.C. Johnston Making of Donald Trump 190: Trump would later brag that he proposed that Kashiwagi [...] come to the Trump Taj Mahal casino on the next Pearl Harbor Day, but that was hot air.

2. attrib. use of sense 1.

1917		S. Lewis Job 266: ‘Lot of hot-air females telling me what I can do and what I can’t do’.
1977		in K. Gilbert Living Black 300: It’s just a perk with nothing to do in between hot-air meetings! Na! Self first, self last, that’s the trouble.

In compounds

hot-air artist (n.) [-artist sfx/merchant n.]

a loquacious person, a person who talks nonsense.

1911		C. Lorenz Tom L. Johnson, Mayor of Cleveland 97: The Senator told the same audiences with all his earnestness, that they had listened to a hot-air artist.
1922		in Some Distinguished Americans 152: He don’t know how to make a livin’ at nuthin’. [...] He’s just a hot-air artist.
1935		(con. 1920s) J.T. Farrell Judgement Day in Studs Lonigan (1936) 537: I do know that Ike [...] is one first rate hot air artist.
c.1943		‘Bill O. Lading’ You Chirped a Chinful!! n.p.: Feather Merchant: Hot air artist.
1959		A. Zugsmith Beat Generation 84: For the sake of melodrama, that hot-air artist would call his own brother a rapist.
2005		M.L. Colley A Summer Story 55: I know, you’re [sic] pop’s the biggest hot air artist in the city, county and state of new York.

In phrases

chew hot air (v.)

to talk nonsense.

1913

J. London Valley of the Moon (2004) 6: Look at your brother, a-runnin’ around to socialist meetin’s, an’ chewin’ hot air.