Acosmism, in contrast to pantheism, denies the reality of the universe, seeing it as ultimately illusory, (the prefix "a-" in Greek meaning negation; like "un-" in English), and only the infinite unmanifest Absolute as real. Conceptual versions of Acosmism are found in eastern and western philosophies.
The Collaborative International Dictionary
Acosmism \A*cos"mism\, n. [Gr. 'a priv. + ? world.] A denial of the existence of the universe as distinct from God.
n. A denial of the existence of the universe as distinct from God.