The Collaborative International Dictionary of English v.0.48:
Sotto voce \Sot`to vo"ce\ [It.] 1. (Mus.) With a restrained voice or moderate force; in an undertone. [1913 Webster] 2. Spoken low or in an undertone. [1913 Webster]WordNet (r) 3.0 (2006):
sotto voce adv 1: in an undertone; "he uttered a curse sotto voce" [syn: sotto voce, in a low voice]