(1) A lump or aggregation of coherent material. SYN: massa [TA]. (2), pharmacotherapy a soft solid preparation containing an active medicinal agent of such consistency that it can be divided into small pieces and rolled into pills. (3) One of the seven fundamental quantities in the SI; its unit is the kilogram, defined as the mass of the international prototype of the kilogram, which is made of platinum-iridium and maintained at the International Bureau of Weights and Measures. (4) The quantity of matter in a body or substance. (5) In pulmonary radiology, a lung or pleural lesion larger than 30 mm in diameter, as inferred from an opacity on the x-ray image; most often a neoplasm. (6) Commonly used as a synonym for tumor or neoplasm. [L. massa, a doughlike mass]