Pertaining to the hours of darkness; opposite of diurnal (1). [L. nocturnus, of the night]
* * *
noc·tur·nal näk-'tərn-əl adj
1) of, relating to, or occurring at night <\nocturnal myoclonus>
2) characterized by nocturnal activity <a \nocturnal form of filariasis>
* * *
noc·tur·nal (nok-turґnəl) [L. nocturnus] pertaining to, occurring at, or active at night.Medical dictionary. 2011.