From Longman Dictionary of Contemporary EnglishRelated topics: Chronologysun-upˈsun-up noun [uncountable]old-fashionedTMCsunriseExamples from the Corpussun-up• These are dusk to around 1.30 a.m., and from first glimmer of light to an hour or so after sun-up.• To reach this desolatespot you set off at sun-up and head toward mountainranges which scarcely ever get closer.• They slipped away just before sun-up.• We have spent two whole days from sun-uptill sun-down in raptconversation.• Probably since sun-up, and he would not stop until it was too dark to work any longer.• It would be dawn soon, then sun-up, and he did not know what he would see.