Out of circulation refers to something that is no longer being distributed or used. Some synonyms for this term include discontinued, obsolete, phased out, removed from circulation, withdrawn, and retired. These terms apply to various contexts, such as books, currencies, technology, and products. Discontinued products or services are no longer available for purchase or use, while obsolete technologies are no longer considered useful or relevant. Similarly, phased-out products or currencies are gradually being replaced by newer alternatives. On the other hand, withdrawn or retired items have been officially taken out of use or circulation. All these terms describe the state of something that is no longer available or usable in the present.