The antonyms for the word "tight-mouthed" are talkative, communicative, expressive, frank, garrulous, loquacious, open, outgoing, verbose, and wordy. Talkative people are those who love to speak their mind and thoughts out loud without any hesitation or restrictions. They are expressive and open about their feelings, emotions, and opinions. In contrast, tight-mouthed people don't reveal their ideas or feelings quickly but keep them hidden. Being communicative is all about engaging in conversations and discussions at the right time with others. It's essential that you pay attention to your surroundings while anything you are going to reveal so it won't hurt yourself or anyone else.