Green’s Dictionary of Slang

1. (US drugs/prison) a means of smuggling drugs into prison: a letter is soaked in some form of narcotized solution and the text of the letter makes it clear, with simple codes, that this has been done [write v. (2)].

1936		D. Maurer ‘Argot of the Und. Narcotic Addict’ Pt 1 in AS XI:2 127/2: writing. 1. A letter written on porous woodpulp paper which has first been soaked in a saturated solution of drug. The letter is mailed to a prisoner and statements in it like ‘Helen asked about you,’ ‘Carrie is in town,’ or ‘Mildred still loves you,’ inform the recipient that heroin, cocaine, or morphine respectively has been put in writing. He may then soak out the drug, cook down the resulting solution, and fill his hypodermic.
1959		J.E. Schmidt Narcotics Lingo and Lore.

2. (US drugs) a narcotics prescription [write v. (2)].

1936		D. Maurer ‘Argot of the Und. Narcotic Addict’ Pt 1 in AS XI:2 127/2: writing. [...] 2. A prescription for narcotics.
1959		J.E. Schmidt Narcotics Lingo and Lore.

3. graffiti [writer n. (1)].

1999		Observer Mag. 26 Sept. 28: The Bronx’s inimitable graffiti, which its practitioners insisted on calling simply ‘writing.’.
2008		‘Grandmaster Flash’ Adventures 32: ‘[M]y writing style was foul, and my name wasn’t getting around. I wasn’t beefin’ with other writers or taking any other risks to get a rep’.