Adj. | 1. | diurnal - belonging to or active during the day; "diurnal animals are active during the day"; "diurnal flowers are open during the day and closed at night" Antonyms: nocturnal - belonging to or active during the night; "nocturnal animals are active at night"; "nocturnal plants have flowers that open at night and close by day" |
2. | diurnal - having a daily cycle or occurring every day; "diurnal rhythms"; "diurnal rotation of the heavens"; "the diurnal slumber of bats" |