Sound off is a common phrase that generally means to speak up or express oneself in a bold and assertive manner. It is often used in military settings, but it's also commonly used in everyday conversation. There are several synonyms for the phrase sound off, including speak out, speak up, voice one's opinion, express oneself, and state one's views. These synonyms all convey the same sense of assertiveness and confidence in expressing oneself or one's ideas. Using synonyms for sound off can add variety to your communication and make your language more engaging and powerful.