noc ‧ tur ‧ nal /nɒkˈtɜːnl $ nɑːkˈtɜːr-/ BrE AmE adjective
[ Date: 1400-1500 ; Language: Late Latin ; Origin: nocturnalis , from Latin nocturnus 'by night' , from nox 'night' ]
1 . an animal that is nocturnal is active at night:
Hamsters are nocturnal creatures.
2 . formal happening at night:
Rebecca paid a nocturnal visit to the flat.