The Collaborative International Dictionary
Sordine
Sordine \Sor"dine\ (? or ?; 277), n. [It. sordina, sordino, from sordo deaf, dull-sounding, L. surdus. See Surd.] (Mus.) See Damper, and 5th Mute.
Wiktionary
sordine
n. A mute for musical instruments. For example, the mute instrument for the violin or the damper on the pianoforte.