Yes, secretest is a Scrabble word!

Adjective

1. Not open or public; kept private or not revealed

2. Conducted with or marked by hidden aims or methods

3. Not openly made known

4. Communicated covertly

5. Not expressed

6. Designed to elude detection

7. Hidden from general view or use

8. (of information) given in confidence or in secret

9. Indulging only covertly

10. Having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding

11. The next to highest level of official classification for documents