What is the meaning of Nocturnal?

Primarily active during the night.

Taking place at night, nightly.

A person or creature that is active at night.

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

nocturnal

Pre-reform spelling (used until 1943 in Brazil and 1990 in Portugal) of noturnal. Still used in countries where the agreement hasn't come into effect; may occur as a sporadic misspelling.

Source: wiktionary.org