What is "psycho-biddy"

Psycho-biddy is a colloquial term for a subgenre of the horror/ thriller movie that features a formerly-glamorous older woman who has become mentally unbalanced and terrorizes those around her. The genre officially began in 1962 with the film What Ever Happened to Baby Jane? (though it had some antecedents) and lasted through the mid-1970s. It has also been referred to by the terms Grande Dame Guignol, hagsploitation and hag horror. Renata Adler, in her The New York Times review for the 1968 film The Anniversary, referred to the genre as "the Terrifying Older Actress Filicidal Mummy genre."