Definition of "nocturnal" in English

adjective

1. (of a person, creature, group, or species) Primarily active during the night.

   • nocturnal birds

2. (of an occurrence) Taking place at night, nightly.

   • a suspicious nocturnal outing

noun

1. A person or creature that is active at night.

2. (historical) A device for telling the time at night, rather like a sundial but read according to the stars.