torus

noun

• A topological space which is a product of two circles.

  "A 4-variable Karnaugh map can be thought of, topologically, as being a torus."

• The standard representation of such a space in 3-dimensional Euclidean space: a shape consisting of a ring with a circular cross-section: the shape of an inner tube or hollow doughnut.
• (in combination, n-torus, 4-torus, etc.) The product of the specified number of circles.
• A molding which projects at the base of a column and above the plinth.
• The end of the peduncle or flower stalk to which the floral parts (or in the Asteraceae, the florets of a flower head) are attached; receptacle, thalamus.
• A rounded ridge, especially one on the occipital bone.