decrescendo

nouns

(music) a gradual decrease in loudness
decrescendo, diminuendo

verbs

grow quieter
"The music decrescendoes here"
decrescendo
antonym
crescendo
is a type of (narrower)
decrease in size, extent, or range
"The amount of homework decreased towards the end of the semester"; "The cabin pressure fell dramatically"; "her weight fell to under a hundred pounds"; "his voice fell to a whisper"
decrease, diminish, fall, lessen

adjectives

gradually decreasing in volume
decrescendo, diminuendo