Cyst

Noun

 * 1) A pouch or sac without opening, usually membranous and containing morbid matter, which develops in one of the natural cavities or in the substance of an organ.

Thesaurus
benign tumor, boil, bump, bunion, callosity, callus, cancer, carbuncle, carcinoma, corn, dilatation, dilation, distension, edema, excrescence, fungosity, fungus, furuncle, growth, intumescence, lump, malignant growth, metastatic tumor, mole, morbid growth, neoplasm, nevus, nonmalignant tumor, outgrowth, pimple, pock, proud flesh, pustule, rising, sarcoma, sebaceous cyst, swell, swelling, swollenness, tumefaction, tumescence, tumidity, tumor, turgescence, turgescency, turgidity, verruca, wart, wen