/ nɒkˈtɜːnl; NAmE nɑːkˈtɜːrnl/ adjective
1.
( of animals ) active at night
OPP diurnal
2.
( formal ) happening during the night :
a nocturnal visit
••
WORD ORIGIN
late 15th cent.: from late Latin nocturnalis , from Latin nocturnus of the night, from nox, noct- night.