from The American Heritage® Dictionary of the English Language, 4th Edition
- adv. Music With moderate volume or in a subdued tone. Used chiefly as a direction.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adv. With a medium fullness of sound.
from the GNU version of the Collaborative International Dictionary of English
- With a medium fullness of sound.
Italian : mezza, half + voce, voice.(American Heritage® Dictionary of the English Language, Fourth Edition)
Italian, from mezzo, feminine mezza ("middle, half") + voce ("voice"). (Wiktionary)