noun (n)

• the time in the evening at which the sun begins to fall below the horizon(noun.time)

  Synonym:
  sunset
  Antonym:
  aurora, break of day, break of the day, cockcrow, dawn, dawning, daybreak, dayspring, first light, morning, sunrise, sunup
  

  source: wordnet30
• The setting of the sun; sunset.(noun)

  source: webster1913