Victorian is the quality of emulating Victorian society from Earth's 19th century. Such elements include; reservations or rigidity regarding the topic of sexuality, the beginnings of industrialization, classic Gothic style architecture and attire among others.
In 2373, while attempting to treat the ravages of pon farr in Ensign Vorik, The Doctor mentioned that Vulcan attitudes toward sex was very Victorian as Vulcans found it distasteful to discuss such matters openly. (VOY: "Blood Fever")
Captain Kathryn Janeway's gothic holonovel Janeway Lambda one, Doctor Beverly Crusher's Orient Express simulation as well as Data's A Christmas Carol simulation were also set during the Victorian era. (VOY: "Cathexis", et al, TNG: "Devil's Due", TNG: "Emergence")