noun, na-adjective, noun which may take the genitive case particle 'no'
privacy; secrecy; confidentiality
Used for matters kept private or secret, often in formal or business contexts. Can be used as a noun or adjectivally with な or の.
この話は内密にしてください。
Please keep this matter confidential.
内密の情報が漏れた。
Confidential information was leaked.