Definition of siderism in US English:

siderism

noun

historical
  • A hidden force or influence to which have been attributed the motions of divining pendulums and other phenomena of animal magnetism.

Origin

Mid 19th century. From German Siderismus (J. W. Kieser Der Siderismus; from ancient Greek σίδηρος iron + -ismus), with alteration of the ending after -ism.