A person who is habitually up or out at night, esp. to socialize. Formerly: spec. †a nocturnal thief (obsolete).
a person who steals by night.
A person, esp. a criminal, who works at night. Cf. moon's man n. at moon, n.1 compounds 2. Obsolete. rare.
A person who is up or active at night for predatory purposes; spec. a nocturnal attacker or thief.