low-key
adjectiveUK /ˌləʊˈkiː/
US /ˌloʊˈkiː/
Not loud or fancy; calm and simple.
We had a low-key birthday party at home with just a few friends.
OTHER MEANINGS
2. Not bright or strong in color or light.
The room was painted in low-key colors like gray and beige.
3. Keeping something secret or not drawing attention to it.
He kept his plans low-key until everything was ready.
4. In a calm, quiet, or slightly relaxed way (informal adverb).
She low-key hoped it would rain so the game would be canceled.