An inexact term referring to organic brain disorder of any degree.
Some authors use the term in a more restricted sense to refer to chronic brain disease with irreversible pathological changes; others use it to describe an acute delirium. Still others use it for early signs of brain tissue dysfunction that are too subtle to warrant a definitive diagnosis.

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