The development of tolerance to a substance, to which the individual has not previously been exposed, as a result of acute or chronic intake of another substance.
The two substances usually, but not invariably, have similar pharmacological effects.
Cross-tolerance is apparent when a dose of the novel substance fails to produce the expected effect.

World Health Organization. Lexicon of alcohol and drug terms published by the World Health Organization. Internet. Accessed on August 20, 2009.