sunset /ˈsʌnˌsɛt/noun 5verb 1forms 3phrases 1 noun5 •the moment at the end of the day when the sun drops out of sight in the west’Twas sunset: when the sun will part There comes a sullenness of heart To him who still would look upon The glory of the summer sun. — 1829 •The changes in color of the sky before and after sunset. •[before a noun] A set termination date.The tax increase legislation included a sunset clause requiring renewal to prevent the tax increase from expiring. •(figurative) The final period of the life of a person or thing.one's sunset years •The region where the sun sets; the west. verb1 •To phase out.We’ll be sunsetting version 1.9 of the software shortly after releasing version 2.0 next quarter. formssunsetted · sunsetting · sunsets Phrases with sunset ride off into the sunsetTo depart and fade into obscurity.