A political philosophy expressing the belief that modern society has erred in many significant ways and—worse—is no longer self-correcting. Adherents advocate a return to moral, political, aesthetic, etc views of earlier times. Victorian England is a common exemplar.
The politics of this group are more or less radioactive. Reactionists are often charged with racism, sexism, and bigotry, since their views include claims that Black Americans fare worse than other minority groups due to deficits in their culture; that women in historic societies were happier in many ways; that our immigration policies make it difficult to maintain cultural capital; etc.
See Alexander - Reactionary Philosophy In An Enormous, Planet-Sized Nutshell for an attempted Steelman argument.