Down:
1. Supercilious: Behaving or looking as though one thinks one is superior to others; haughty.
2. Propinquity: The state of being close to someone or something; proximity.
3. Placate: To make (someone) less angry or hostile; to calm or soothe.
4. Solecism: A grammatical mistake in speech or writing; a breach of good manners or etiquette.
6. Pulchritudinous: Describing physical beauty, often used to describe someone's appearance in an elegant or literary way.
9. Panacea: A solution or remedy for all difficulties or diseases; a universal cure.
Across:
5. Surreptitious: Kept secret, especially because it would not be approved of; stealthy.
7. Perfidious: Deceitful and untrustworthy; treacherous
8. Sempiternal: Eternal and unchanging; everlasting.