n. 1 any disorder of the metabolism with excessive thirst and the production of large amounts of urine. 2 (in full diabetes mellitus) the commonest form of diabetes in which sugar and starch are not properly absorbed from the blood, with thirst, emaciation, and excessive excretion of urine with glucose. diabetes insipidus a rare metabolic disorder due to a pituitary deficiency, with excessive urination and thirst.
[ orig. = siphon: L f. Gk f. diabaino go through ]