What is "berserk!"

Berserk! (also known as Circus of Blood) is a 1967 British horror- thriller film starring Joan Crawford, Ty Hardin, and Judy Geeson in a macabre mother-daughter tale about a circus plagued with murders. The screenplay was written by Herman Cohen and Aben Kandel, and the film directed by Jim O'Connolly. Berserk! marks Crawford's second-to-last big-screen appearance.