Pronunciation: (sol'um),[key] —adj. 1. grave, sober, or mirthless, as a person, the face, speech, tone, or mood: solemn remarks. 2. gravely or somberly impressive; causing serious thoughts or a grave mood: solemn music. 3. serious or earnest: solemn assurances. 4. characterized by dignified or serious formality, as proceedings; of a formal or ceremonious character: a solemn occasion. 5. made in due legal or other express form, as a declaration or agreement: a solemn oath. 6. marked or observed with religious rites; having a religious character: a solemn holy day. 7. uttered, prescribed, or made according to religious forms: a solemn ban on sacrifice.