Green’s Dictionary of Slang

(drugs) an injection of narcotics.

1967		Maurer & Vogel Narcotics and Narcotic Addiction (3rd edn).
1973		E. Bunker No Beast So Fierce 268: Let me get my outfit. I’ll need a geez before I get back.
1976		M. Braly False Starts 241: Do a little geeze and lay back to dig the sounds.
1981		E. Bunker Little Boy Blue (1995) 283: ‘I thought you had a getup fix.’ ‘Yeah, one chickenshit geeze.’.