Derived from objet trouvé (found object) in dadaism, a found sound is one taken out of its original context and re-contextualised within a musical context. This is particularly easily done within the genre of electroacoustic music.
Bibliography: Hannemann, Beate (1999). Tod dem Mondschein (Death of the moonlight)
Welsh, John (1985). Music in the Air. A Radio Landscape - Here and There