1. A lack of transparency; an opaque or nontransparent area. 2. On a radiograph, a more transparent area is interpreted as an o. to x-rays in the body. 3. Mental dullness. [L. opacitas, shadiness]
nodular o. a solitary, round, circumscribed shadow found in the lung on chest radiograph; causes include granuloma, primary or metastatic carcinoma, benign tumor, vascular malformation.coin lesion of lungs;
snowball o. a spherical, white body seen in the vitreous in asteroid hyalosis.
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