Green’s Dictionary of Slang

1. cocaine base, purified by ether and smoked rather than sniffed or injected.

1980		cited in Spears Sl. and Jargon of Drugs and Drink (1986).
1989		(con. 1982–6) T. Williams Cocaine Kids (1990) 5: When base (or ‘freebase’) first appeared in the late 1960s, users rolled it into marijuana joints or cigarettes. [Ibid.] 39: Many users had grown tired of sniffing cocaine, and sought out the best and most efficient high, which – they were convinced – meant ‘rock’ they could cook into freebase for themselves.
1992		T. Williams Crackhouse 4: Freebase, or ‘base,’ is cocaine with the hydrochloride removed, a process that involves reducing the powdered cocaine to a rock-like substance ready for smoking. Crack is similar, but one or more chemicals are added in its manufacture.
1998		C. Fleming High Concept 119: James’ freebase cocaine habit had driven him into a $12,000 debt.
2002		‘Touré’ Portable Promised Land (ms.) 155: We Words (My Favorite Things) [...] Tical. Freebase. Maryjane. Moonrock.

2. in attr. use of sense 1.

2010

K. Richards Life 434: There was a big freebase party going on.

3. crack cocaine.

2001		J. Stahl Plainclothes Naked (2002) 145: The voice was frantic, quavery. A tweaker. When her first husband [...] got deep into freebase, he sounded the same way.
2003		Mad mag. July 29: ‘Oh #$*!’ moans the incorrigible freddy freebase as he wadddles down the back alleys [...] looking for a fix [...] There’s not much he won’t do to score some rocks.
2007		(ref. to 1980s) N. ‘Razor’ Smith Raiders 175: Crack cocaine or ‘freebase’, as it was known in those days.