sunsetsun·set /ˈsʌnset/ adjectiveadj [only before a noun]1ECONOMICS no longer very profitable or important and based on old TECHNOLOGIESAs their profit levels fall, these new industries, in their turn, will become sunset sectors.
2LAWsunset rules or laws are ones which cancel rules or laws that were made in the pastThe new sunset law will eliminate statutes that are more than 10 years old.
Thesunset provisions will cancel most tax increases since June 30.