(architecture) A round building, usually small, often with a dome.

The United States Capitol rotunda.

plural of rotunda

A small round building, completely open at the sides and without walls, where a band of musicians can play to an audience. Usually situated in a public park.

(typography) A curved form of the letter r, found in some medieval and fraktur scripts: ⟨ ꝛ ⟩.

plural of band rotunda