A na-adjective meaning secretive or private, indicating something done quietly, privately, or without others knowing.
彼女は密かに留学を決めていた。
She had secretly decided to study abroad.
密かな楽しみは、毎晩少しだけ好きな本を読むことだ。
My secret pleasure is reading a little of my favorite book every night.
二人は密かに連絡を取り合っていた。
The two of them were communicating secretly.