(Science: disease) (gr. Diabetes a syphon, from dia through _ bainein to go) a general term referring to disorders characterised by excessive urine excretion (polyuria), as in diabetes mellitus and diabetes insipidus. When used alone, the term refers to diabetes mellitus. Any of several metabolic disorders marked by excessive urination and persistent thirst.The are two types of diabetes. Diabetes mellitus involves irregular blood sugar concentration, where a lack of insulin results in excess sugar in the bloodstream and urine, due to the fact that it is not being stored as glycogen where it can be used on-demand. The other type of diabetes, diabetes insipidus, results in excess urine being excreted by the sufferer.