Voiced

A speech sound is called voiced if during its pronunciation the vocal folds are brought close together so that air flowing between them causes them to vibrate.

Example
In English [b] and [d] are [+voiced] as opposed to [p] and [t] which are [-voiced], i.e. voiceless.

Antonym

 * voiceless

other languages
German stimmhaft

Links
Utrecht Lexicon of Linguistics