1. A room or porch exposed by the sun: "Karl enjoys sitting in his solarium in the morning while he is eating his breakfast and reading the newspaper."
2. A room designed for solar therapy or heliotherapy which is a medical treatment using the sun's rays: "One of the treatments which Shareen's uncle received during his stay at the sanitarium was a daily visit to the solarium where he could sit comfortably in the warm sunshine."
3. A day, or recreational room in a hospital or medical setting for patients that is often used as a waiting area for families or visitors: "When Josh and his family visited his uncle at the sanatorium, they usually waited for him in the sunny solarium there were also many beautiful plants."