Green’s Dictionary of Slang

1. (drugs) ampoule.

1967		Wentworth & Flexner DAS (Supplement).
1973		Maurer & Vogel Narcotics and Narcotic Addiction (4th edn).

2. an amplifier.

1966		T. Keyes All Night Stand 16: Cass came and banged on the door with the bass amp.
1981		D. Jenkins Baja Oklahoma 20: ‘You a roadie or a groupie?’ ‘What’s the difference?’ ‘They both give blowjobs but a roadie has to carry an amp’ .
1999		(con. 1979–80) A. Wheatle Brixton Rock (2004) 83: There was this big bang and nuff smoke was coming from the amp.
2007		T. Dorsey Hurricane Punch 238: Amp? Like in guitar amp?
2010		K. Richards Life 91: All I could hope for was that my amp would work.

3. (US drugs) amphetamine.

1975		Hardy & Cull Drug Lang. and Lore.
1986		Spears Sl. and Jargon of Drugs and Drink.
2001		ONDCP Street Terms 1: Amp — Amphetamine.

4. methadone.

1983

New Society 11 Aug. 203/1: ‘My mate’s got amps if you wan’ ’em.’ [...] Amps (methadone, a synthetic heroin substitute), Rit (Ratlin, a stimulant) [...] you can get them all on the streets round here.

5. (US drugs) marijuana dipped in formaldehyde, sometimes laced with PCP.

2001		ONDCP Street Terms 1: Amp — [...] marijuana dipped in formaldehyde or embalming fluid, sometimes laced with PCP and smoked.
2014		N. Kolicki ‘Poachers’ in ThugLit Sept. [ebook] Amp, fry—that's east coast hood rat shit. Blunts drenched in phencyclidine and dried out.