Other forms: diminuendos
In music, diminuendo means gradually growing more quiet. When the sheet music calls for a diminuendo, that's definitely not the time to blow your trumpet as hard as you can.
As they play, musicians don't simply follow the notes; musical notation includes a lot of additional information, including how fast to play, whether to be loud or quiet, and when to increase or decrease the volume. Diminuendo, which comes from the Latin root deminuere, or "diminish," instructs a pianist or cellist to quiet their playing, transitioning to a more gentle sound.