akusu-kū

(Jap, wrong understanding of emptiness). In zen Buddhism, a mistaken notion of emptiness (śūnyatā) which regards it as nothingness. Correctly understood, however, śūnyatā is not the the mere negation of existence but the true nature of phenomena. According to the Heart Sūtra, ‘form is not other than emptiness, and emptiness is not other than form’.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)