Green’s Dictionary of Slang

shooter n.2

1. (US drugs, also needle shooter) a heroin or other narcotics addict; occas. attrib.

[US]Howsley Argot: Dict. of Und. Sl. 34: needle shooter–a hypodermic addict.
[US]N. von Hoffman We are the People Our Parents Warned Us Against 65: A mean, crazy-eyed New York scag-shooter.
[US]Illinois Legislative Investigating Committee Drug Crisis in Spears (1986).
[US]R. Sabbag Snowblind (1978) 237: It was the methedrine shooters who were dying all over the Haight in San Francisco [...] in the late 1960s.
[US]C. Stroud Close Pursuit (1988) 269: Muro had been sharing a needle with a shooter on Avenue D.
[US]S. Morgan Homeboy 15: Temples scooped deep as shooter spoons.
[US]Simon & Burns Corner (1998) 7: Rail-thin coke freaks and abscessed shooters press dirty singles and fives into waiting hands.
[US]G. Pelecanos Hell to Pay 233: His mother was welfare dependent and a shooter of heroin and cocaine.
[US]J. Stahl Happy Mutant Baby Pills 205: There were public shooters and there were privates.

2. a hypodermic syringe.

[US]J. Stahl Permanent Midnight 230: You had to break a glass ampoule [...] suck it into the shooter, and jam it into your bunched-up tummy.

3. one injects a third party with narcotics.

[US]J. Stahl Bad Sex on Speed 29: He’s shooting up Penny [...] ‘It’s important,’ she said, while the shooter dabbed her off.