FORTISSIMO Meaning of FORTISSIMO in English [for.tis.si.mo] adv or adj [It, superl. of forte] (1724): very loud--used esp. as a direction in music [2]fortissimo n, pl -mos or -mi (1856): a very loud passage, sound, or tone Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012