Definition of diurnal adjective from the Oxford Advanced American Dictionary

     

    diurnal

     adjective
    adjective
    NAmE//daɪˈərnl//
     
     
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  1. 1(biology) (of animals) active during the day Unlike most other bats, this species is diurnal. opposite nocturnal
  2. 2(astronomy) taking one day the diurnal rotation of the earth
See the Oxford Advanced Learner's Dictionary entry: diurnal