A “cult classic” is a film that wasn’t popular or well regarded in it’s time but has developed loyal following over the years.
80’s films that probably would fall under the cult classic label: Flash Gordon, Motel Hell, Ms .45, Blade Runner, Videodrome, Toxic Avenger, Repo Man, Brazil, The Hitcher, Rad, Near Dark, Barfly, Miracle Mile, Heathers, Killer Klowns from Outer Space, UHF, and so on…