Rebreathe is a term used for the process of inhaling air that has already been exhaled. It is widely used in medical settings to provide patients with a mixture of oxygen and carbon dioxide. Synonyms for the word "rebreathe" include "circulatory respiration," "reinhalation," "recirculation," "reprocessed air," and "re-used air." Other terms that may refer to a similar process include "re-breathing," "re-freshening," "re-cycling," and "re-oxygenating." These synonyms can be used interchangeably to describe the process of inhaling air that has already been exhaled, and are often used in medical and scientific contexts.