Other forms: voicelessly
Someone who can't speak, either literally or figuratively, is voiceless. Your sore throat may leave you voiceless for a couple of days, and the youngest child in a family might feel voiceless when it comes to making to big family decisions.
If you suffer from laryngitis, you're temporarily voiceless, unable to use your voice to speak. Someone who's mute, for a physical or psychological reason, is often permanently voiceless. It's also common to use this adjective for people so powerless that they're unable to express their needs or desires: "Women in that country have been voiceless for a long time, but that's finally beginning to change."