sunsetting

1. The event or time of the disappearance of the upper circumferential edge of the sun as it sets below the horizon. 2. The sky as the sun sets. 3. A decline or final phase. 4. The automatic expiration of a statutory provision on a previously established date, in the absence of reauthorization 1. Providing for an automatic expiration. 2. To expire on a previously established date, as a statutory provision.