(1) Discoid or coin-shaped; denoting the thick mucous or mucopurulent sputum in certain respiratory diseases, so called because of the disc shape assumed when it is flattened on the bottom of a sputum mug containing water or transparent disinfectantor shape of lesions in nummular eczera. (2) Arranged like stacks of coins, denoting the lining up of the red blood cells into rouleaux formation. SYN: nummiform. [ L. nummulus, small coin, dim. of nummus, coin]