Wordnet 3.0
ADJECTIVE (2)
1.
belonging to or active during the night;
- Example: "nocturnal animals are active at night"- Example: "nocturnal plants have flowers that open at night and close by day"2.
of or relating to or occurring in the night;
- Example: "nocturnal darkness"
The Collaborative International Dictionary of English v.0.48:
Nocturnal \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.
[1913 Webster]
2. Having a habit of seeking food or moving about at night;
as, nocturnal birds and insects; raccoons are nocturnal.;
-- of animals.
[1913 Webster +PJC]
The Collaborative International Dictionary of English v.0.48:
Nocturnal \Noc*tur"nal\, n.
An instrument formerly used for taking the altitude of the
stars, etc., at sea. --I. Watts.
[1913 Webster]
WordNet (r) 3.0 (2006):
nocturnal
adj 1: 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" [ant:
diurnal]
2: of or relating to or occurring in the night; "nocturnal
darkness"