Green’s Dictionary of Slang

(drugs) heroin.

1912		Brooklyn Dly Eagle (NY) 15 Sept. 38/5: There seems to be a certain raternal feeling among the users of ‘scat’ [...] a desire to ‘help out’ a victim who is without a supply of ‘scat’.
1915		Marion Star (OH) 3 Apr. 17/6: Heroin is sometimes called ‘scat’ or ‘H’.
1949		Monteleone Criminal Sl. (rev. edn).
1953		Anslinger & Tompkins Traffic In Narcotics 314: scat. Heroin.
1971		E.E. Landy Underground Dict. (1972).
1980		‘Gloss. of Drug Terms’ National Instit. Drug Abuse.
2001		ONDCP Street Terms 19: Scate [...] Scat — Heroin.