gallstoneEnglishOxford New American Dictionarygallstone /ˈɡôlˌstōn, ˈɡɔlˌstoʊn / ▸ noun a small, hard crystalline mass formed abnormally in the gallbladder or bile ducts from bile pigments, cholesterol, and calcium salts. Gallstones can cause severe pain and blockage of the bile duct.