Decrescendo (Italian: growing less) is used as a direction to performers, meaning becoming softer.

1806, from Italian decrescendo, from Latin decrescere (see decrease (v.)).

A directive to a performer  to smoothly decrease the volume of the specific passage. This can be designated with the word decrescendo at the beginning of the passage or with the decrescendo symbol con [..]

(n) (music) a gradual decrease in loudness(v) grow quieter(adj) gradually decreasing in volume

To become softer gradually. Opposite of crescendo.

(decresc.) gradually getting softer  

gradually getting softer

Italian dynamic marking meaning to gradually get softer.

 or decresc. – same as diminuendo or dim. (see below)

gradually becoming softer

gradually getting softer. Notated by the > symbol.

Gradually getting softer (Same as Diminuendo)

   A gradual decrease in loudness or volume level.

A gradual decrease in dynamics, or getting quieter.

(decresc., decres.) [It] gradually getting softer.

Another Italian word meaning gradually getting softer.  The symbol for Decrescendo is seen in the above diagram on the third line.  It looks like a sideways V gradually closing and moves from playing [..]

Gradually getting quieter

Decrease in volume

becoming softer. The same as diminuendo. See also “dynamics”.