The Collaborative International Dictionary
Free base
Free base \Free" base`\ (fr[=e]" b[=a]s`), n.
(Chem.) The basic form of an organic amine which is capable of forming acid salts such as hydrochlorides.
The basic form of a drug, often more powerful than a salt form because it is more readily absorbed into the blood stream.
Free base
free-base \free-base\, Free base \Free" base`\(fr[=e]" b[=a]s`), v. i. To ingest the basic form of a narcotic drug, usually by injection.
Wikipedia
Free base
Free base (freebase, free-base) refers to the conjugate base ( deprotonated) form of an amine, as opposed to its conjugate acid ( protonated) form. The amine is usually an alkaloid, such as nicotine, cocaine, morphine, and ephedrine, or derivatives thereof.