Green’s Dictionary of Slang

1. (US) a democrat.

1797		P. Freneau ‘The Royal Cockneys in America’ Collection of Poems on Amer. Affairs (1815) I 38: Why Porcupine Peter, / The democrat-eater, / Transported by Pitt, at the charge of the nation, / To preach to the demo’s a new revelation.
1805		T.G. Fessenden Democracy Unveiled 148: Demo’s and Feds would all be merry.

2. (orig. Aus.) demonstration (of a political or pressure-group nature).

1904		Truth (Sydney) 11 Sept. 7/2: A dig at demos. On a charge of distributing certain handbills advertising a ‘Monster Democratic Demonstration’.
1936		J. Curtis Gilt Kid 28: The anti-war demo last week.
1949		A. Wilson Wrong Set 100: Norman’s out at the demo. At Trafalgar Square.
1958		(con. 1936) A. Wesker Chicken Soup with Barley I i: You won’t see him at any demo.
1968		Listener 28 Mar. 410: The US Embassy provided a focus for an extreme Left ‘demo’ against ‘fascist brutality’ in Vietnam.
1977		K. Gilbert Living Black 93: The golden opportunity for a demo was lost when the Sydney Opera House was opened in 1973.
1989		(con. 1968) P. Theroux My Secret Hist. (1990) 286: We’re going to have a huge demo in Grosvenor Square.
1992		D. Jarman letter 5 Mar. Smiling in Slow Motion (2000) 88: I missed the Outrage! demo.
2003		Eve. News (Edinburgh) 29 Apr. 🌐 [headline] American troops shoot children in Iraqi demo.

3. (also dem, demmo) a demonstration, e.g. of a specific skill or action.

1947		J. Maclaren-Ross Of Love And Hunger 9: [of a door-to-door vacuum salesman] ‘How many dems d’you get today?’ ‘Five. Two of ’em duds.’.
1963–74		B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 38: I might as well give you a demmo.

4. demolition; also as demolition material, i.e. explosives (see cit. 1989).

1943		J. Twist Bombardier [film script] ‘Don’t I get to play with these demos?’ ‘No demolition bombs for you.’ [HDAS].
1960, 1975		Wentworth & Flexner DAS 144/2: demo n. A member of a squad or a squad of demolition workers.
1980		L. Mantell Murder and Chips 69: Yeh. Got turfed out because he lost his cool at the demo.
1989		Hackworth & Sherman About Face (1991) 157: We had enough demo to blow up the Golden Gate.
1990		S. Morgan Homeboy 6: Smashed potted plants contributed to the domestic demo derby.

5. a demonstration record or tape, used to promote a band’s or individual musician’s work [SE demonstration (disc/record/tape)].

1954		Billboard 27 Nov. 14/4: Altho the demo is designed for distributors, it can also be used by dealers; so M-G-M’s distributors will leave the demos with their retail clients for use on the customer level .
1961		H. Ellison Rockabilly (1963) 84: She had, indeed, cut a demo.
1977		Rolling Stone 22 Sept. 37: A couple of demos later, Sam Phillips [...] was looking for a singer to record a song he liked.
1984		C. White Life and Times of Little Richard 121: The main title on the demos, ‘Bama Lama Bama Loo’ recaptured the excitement of Richard’s old hits.
1998		Hip-Hop Connection Dec. 14: The demos they cut for me...were so hot.
2000		W. Shaw Westsiders 14: They [...] took their very first demo to Suge Knight’s Death Row record company.
2011		W.D. Myers Cruisers: Checkmate 2: ‘They’re hiring me on the strength of my demo. I don’t even have to audition’.

6. a car dealer’s demonstration model.

1981

J. Ellroy Brown’s Requiem 19: Larry, the sales manager at Casa, fixed me up with an old Cutlass demo, loaded.