torus

noun (plural tori /ˈtôrī/ or toruses)

• 1 Geometry a surface or solid formed by rotating a closed curve, especially a circle, around a line that lies in the same plane but does not intersect it (e.g., like a ring-shaped doughnut).
• a thing of this shape, especially a large ring-shaped chamber used in physical research.

• 2 Architecture a large convex molding, typically semicircular in cross section, especially as the lowest part of the base of a column.

• 3 Anatomy a ridge of bone or muscle:the maxillary torus

• 4 Botany the receptacle of a flower.