Definition of "solemn"

(religion, specifically Christianity) Of or pertaining to religious ceremonies and rites; (generally) religious in nature; sacred.  examples

(by extension)

1. Characterized by or performed with appropriate or great ceremony or formality.  examples

2. Deeply serious and sombre; grave.  examples

3. Inspiring serious feelings or thoughts; sombrely impressive.  examples

4. (obsolete) Cheerless, gloomy, sombre.