Dictionary.com
Thesaurus.com

mezzo piano

American  
[met-soh pee-ah-noh] / ˈmɛt soʊ piˈɑ noʊ /

adverb

Music.
  1. somewhat louder than piano but softer than forte; moderately soft.


Etymology

Origin of mezzo piano

1805–15; < Italian: literally, half soft