Which Italian term means 'gradually getting louder'?

The Italian term for gradually getting louder is crescendo. In musical notation, it tells performers to increase the volume progressively over a passage rather than becoming louder all at once.

The word comes from the Italian verb crescere, meaning “to grow” or “to increase.” Composers commonly abbreviate it as cresc. or show it with a hairpin-shaped symbol that opens toward the right. The marking can apply to a short phrase or a much longer section of music.

Crescendo is a dynamic change, not a tempo instruction. It affects loudness while leaving the speed of the music to separate markings such as accelerando or ritardando. The opposite dynamic direction is decrescendo, also called diminuendo, which means gradually getting softer.

Pianissimo means very softly, while fortissimo means very loudly; neither describes a gradual change. That distinction is why crescendo is the precise answer even though the other terms also describe musical volume.