noun

1. 1. the daily disappearance of the sun below the western horizon
   2. the varying time of this
   3. the atmospheric phenomena at this time; esp., the color of the western sky at sunset
2. the final phase or decline (of a period)

Etymology: ME sunne set, sonsette: see sunrise

adjective

1. ☆ designating or of a law, bill, etc. requiring that certain government agencies, programs, etc. come to an end after a specified period unless they get legislative approval again
2. designating an industry that is in a final state of decline, as because of a diminished use of its products or an inability to meet foreign competition