1. of or pertaining to the night.
2. done, occurring, or coming at night: nocturnal visit.
3. active at night: nocturnal animals.
4. opening by night and closing by day, as certain flowers.
Now, what is the opposite of Nocturnal?
Answer: Diurnal is the opposite of nocturnal. It describes animals that are active during the day.
Example of animals that are active during night time: