A person who lends their voice for recording, often for
animation.
Mel Blanc was one of these, for
Warner Bros.'
Looney Tunes cartoons. They are also hired for video games, narrators in commercials, unseen radio announcers in movies, and things of that sort.
As an interesting note, many companies hire
Canadian voice actors over American ones, because they're significantly cheaper.
Capcom does this, for example, in their
Resident Evil games; nobody seems to be able to pronounce Raccoon City/raccoon properly. ;)