Definition of freebases:
(n) :
(specifically) The purified, dry form of certain illegal drugs, especially cocaine.
(v) :
To use a purified drug, especially cocaine, by heating it and inhaling the fumes produced.
(n) :
(chemistry) The purified, dry form of an amine, especially an alkaloid natural product, that is normally used in solution.
(v) :
To purify a drug by crystallization.