n.1. a. A roof or vault having a circular, polygonal, or elliptical base and a generally hemispherical or semispherical shape.
b. A geodesic dome.
2. A domelike structure or object.
3. Geology Any of various natural structures having a rounded shape, especially:
a. A system of strata that is uplifted in the center, forming a concentric anticline.
b. A mass of granite that has been weathered into a rounded shape by exfoliation.
c. A mound formed by the extrusion of viscous lava from a volcano.
4. Chemistry A form of crystal with two similarly inclined faces that meet at an edge parallel to the horizontal axis.
5. Slang The human head.
6. Archaic A large, stately building.