A pseudocoelom is a body cavity that surrounds the tissue of the endoderm layer of the cell. However unlike the true coelom or eucoelom derived as a cavity in the mesoderm and lined by mesothelium, a pseduocelom is just a persistent blastocoelic cavity of the early embryo & is not lined by any mesothelium. Phyla nematoda and rotifera are examples of animals with pseudocoeloms. These pseudocoeloms are the animal's body cavity.
Animals with pseudocoeloms are generally referred to as pseudocoelomates. This is no longer believed to be a valid taxonomic category, but is still used as a descriptive term.