Main Entry: lac·co·lith

Pronunciation: \ˈla-kə-ˌlith\

Function: noun

Etymology: Greek lakkos pond, reservoir + English -lith — more at lake

Date: 1879

: a mass of igneous rock that is intruded between sedimentary beds and produces a domical bulging of the overlying strata

— lac·co·lith·ic \ˌla-kə-ˈli-thik\ adjective