freebase

/F R IY1 B EY0 S/
noun
  1. 1

    The purified, dry form of an amine, especially an alkaloid natural product, that is normally used in solution.

  2. 2

    (specifically) The purified, dry form of certain illegal drugs, especially cocaine.

verb
  1. 1

    To purify a drug by crystallization.

  2. 2

    To use a purified drug, especially cocaine, by heating it and inhaling the fumes produced.

Source: https://en.wiktionary.org/wiki/freebase