Green’s Dictionary of Slang

pinhead n.

[SE pin + -head sfx]

1. in US drug uses.

(a) a small pill of opium, costing 25 cents.

[US]S. Crane in Sun (N.Y.) 20 Oct. in Stallman (1966) 144: The ordinary smoker consumes 25 cents’ woth of opium each day [...] The ordinary smoker is satisfied with pinheads. Pinheads are about the size of a French pea.

(b) one who injects narcotics, esp. when using a rudimentary syringe based on a pin and medicine dropper.

[US]Irwin Amer. Tramp and Und. Sl. 146: Pinhead.–A drug addict.
[US]Monteleone Criminal Sl. (rev. edn).
[US]J.E. Schmidt Narcotics Lingo and Lore.
[US]Ragen & Finston World’s Toughest Prison 812: pinhead – A drug addict.
[UK]G. Fletcher Down Among the Meths Men 51: Pinhead Flynn and Sidney the Sod are [...] out on the rampage tonight.

(c) an amphetamine user.

[US]E.E. Landy Underground Dict. (1972).
[US]Ramones [song title] Pinhead.

(d) a very thin marijuana cigarette.

[US]R.R. Lingeman Drugs from A to Z (1970).
[US]J. Homer Jargon.

2. (orig. US) a stupid person.

[US]Ade Artie (1963) 3: I’ve got as much right to go out and do the heavy as any o’ you pin-heads.
[US]Comic Section N.-Y. American and Journal 21 Jan. 1: It is a frightful bore to children [...] sitting about with pin heads and gossips.
[US]Van Loan ‘Crossed “Signs”’ in Lucky Seventh (2004) 262: He was a pinhead [...] And anybody knows that you can’t learn a pinhead nothing.
[UK]Wodehouse Inimitable Jeeves 86: The poor, misguided pinhead.
[US]J. Lait Gangster Girl 85: You’re no pinhead, Annie. That’s a pretty profound analysis.
[US]F.S. Fitzgerald ‘No Harm Trying’ in Pat Hobby Stories (1967) 125: Miss Starheim has turned out to be a pinhead.
[Aus](con. 1940s) E. Lambert Veterans 109: Never mind, pin-head.
[UK]P. Barnes Ruling Class I xvi: He’s only a bleery-eyed blooster, an English pinhead.
[US]L. Bangs in Psychotic Reactions (1988) 230: Gobbing: [...] Listen ya little pinheads, it’s nauseating and moronic.
[US]E. Bogosian Talk Radio (1989) 54: Your brother’s a creep and a pinhead just like you are.
[UK]Indep. Rev. 3 June 2: Another self-indulgent, over-privileged pinhead with a junk problem.
[US]C. Hiaasen Nature Girl 169: What a fucking pinhead.

3. (orig. US) a person with a small head.

[US]A. Baer Two & Three 19 Mar. [synd. col.] At the height of 5,000 foot rulers all the players looked like pinheads.
E. Seago Sons of Sawdust 219: Pinheads, freaks in a side-show .
[Aus]R. Rivett Behind Bamboo 398/2: Pinhead, one with a small head.
[US]‘Iceberg Slim’ Pimp 64: There was something familiar about that small pin head driver.
[US]M. Leyner Et Tu, Babe (1993) 25: My heart went out to Joe — tiny mishapen ‘pinhead,’ flipper-like forearms.
[Ire](con. 1919) R. Doyle A Star Called Henry (2000) 279: And the best of Ireland’s freaks [...] pinheads, hunchbacks, dwarfs.