Another term for ectoplasm, a substance claimed to issue
from the body of a materialization medium in a vaporous or
solid form, taking on the appearance of phantom forms or
limbs. The concept of ideoplasm stems from the investigations
of such psychical researchers as the Frenchman Gustav Geley
and conveys the additional idea that the substance may be
molded by the operators into any shape to express ideas of the
medium or of the sitters.