free base
noun(free-base)
a purified solid form of cocaine (such as crack) that is obtained by treating the powdered hydrochloride of cocaine with an alkaloid base (such as sodium bicarbonate) and that can be smoked or heated to produce vapors for inhalation; specifically : a form derived from treatment of the hydrochloride of cocaine with ammonia or similar alkaloid solution followed by extraction with a solvent (such as ether)