Having an import not apparent to the senses nor obvious to the intelligence

• Not open or public
• Beyond ordinary understanding
• Any of various organs that synthesize substances needed by the body and release it through ducts or directly into the bloodstream
• Kept private or not revealed
• Hidden from general view or use
• Squirrel, at times
• Not expressed
• Not openly made known

Wiktionary Word definitions in Wiktionary
n. (alternative spelling of secretor English)