1Just and honest conduct, especially (in later use) with regard to business affairs; equitable treatment of others.
2In copyright law: the exception to the law of infringement allowing, in certain circumstances, excerpts of copyrighted material to be quoted without the permission of the copyright holder, for purposes such as private study, research, or criticism; an instance of this.
Especially in use in the jurisdictions of the United Kingdom and Commonwealth countries.
Early 17th century; earliest use found in William Barlow. From fair + dealing.