Mute means unable to speak. In my early days of role-playing on City of Heroes (may a chorus of mighty baritone angels sing her to eternal sleep), I rolled a sonic blaster who couldn't speak without unleashing a torrent of destruction. Fun on paper, most annoying RP ever for everyone involved.
See! I'm not the only one!
Mute character = Bad.
Mute character + slow and/or overly verbose typists = Spawn of satan.