| a person who often stays up late at night; nighthawk. |

| night owl n. Informal A person who habitually stays up and is active late into the night. |
night owl
A person who habitually stays up late and is active at night, as in You can call her after midnight, for she's a night owl. This colloquial term, originally used in the late 1500s for an owl that is active at night, was transferred to nocturnal human beings in the mid-1800s.