laccolithEnglishOxford New American Dictionarylaccolith /ˈlakəˌliTH, ˈlækəˌlɪθ / ▸ noun Geology a mass of igneous rock, typically lens-shaped, that has been intruded between rock strata causing uplift in the shape of a dome. – ORIGIN late 19th century : from Greek lakkos ‘reservoir’ + -lith.