1. a literary or scientific institution, society, or reading room; a building housing a library or museum
Usage: often capitalized when referring to a specific institution; chiefly historical or formal

Examples

• The Boston Atheneum is one of the oldest membership libraries in the United States.
• Members of the atheneum gathered to discuss the latest scientific discoveries.
• The town's atheneum served as a center for intellectual and cultural activities.
• She spent her afternoons reading at the local atheneum.
• The atheneum housed an impressive collection of rare books and manuscripts.