An appliance or device for a particular purpose: an x-ray apparatus. An integrated group of materials or devices used for a particular purpose: dental apparatus. See Synonyms at equipment. The totality of means by which a designated function is performed or a specific task executed, as in a system of government. A political organization or an underground political movement. Also called apparat. Physiology A group or system of organs that collectively perform a specific function or process: the respiratory apparatus; the digestive apparatus. The critical and source material, usually including notes and a glossary, that accompanies a scholarly edition of a text.