Pronunciation: (nok-tûr'nl),[key] —adj. 1. of or pertaining to the night (opposed to diurnal).
2. done, occurring, or coming at night: nocturnal visit. 3. active at night (opposed to diurnal): nocturnal animals. 4. opening by night and closing by day, as certain flowers (opposed to diurnal).
—n. Archaic.an astrolabe for telling time at night or for determining latitude by the position of certain stars in reference to Polaris.