From WordNet (r) 3.0 (2006):
sunset
adj 1: of a declining industry or technology; "sunset
industries"
2: providing for termination; "a program with a sunset
provision"
n 1: the time in the evening at which the sun begins to fall
below the horizon [syn: sunset, sundown] [ant:
aurora, break of day, break of the day, cockcrow,
dawn, dawning, daybreak, dayspring, first light,
morning, sunrise, sunup]
2: atmospheric phenomena accompanying the daily disappearance of
the sun
3: the daily event of the sun sinking below the horizon