fortissimo UK /fɔːˈtɪsɪməʊ/US /fɔɹˈtɪsɪmoʊ/adverb 1noun 1forms 4 adverb1 •Indicating that the piece is to be played very loudly. noun1 •The dynamic sign indicating that the piece should be played fortissimo. formsfortissimi · fortissimos · more fortissimo · most fortissimo
