Noc*tur"nal (?), a. [L. nocturnalis, nocturnus, fr. nox, noctis, night. See Night, and cf. Nocturn.] 1. Of, pertaining to, done or occuring in, the night; as, nocturnal darkness, cries, expedition, etc.; -- opposed to diurnal. Dryden.

2. Having a habit of seeking food or moving about at night; as, nocturnal birds and insects.

Noc*tur"nal, n. An instrument formerly used for taking the altitude of the stars, etc., at sea. I. Watts.

• Primarily active during the night.