Green’s Dictionary of Slang

greasy adj.2

[grease n.1 (2b)]

(US drugs) concerning drugs and their sale.

[US] personal communication in Spears Sl. and Jargon of Drugs and Drink (1986).

In compounds

greasy bag (n.) [bag n.1 (7)]

(US drugs) a bag in which heroin is transported and/or sold.

Probert Encyc. 🌐 Greasy bag is American slang for a bag in which heroin is transported or sold.