In text messages, MB most commonly means my bad. People use it as a quick way to apologize for a mistake, misunderstanding, or accidental action. For example, someone might text, “MB, I forgot to reply,” meaning “My bad, I forgot to reply.” The abbreviation is informal and commonly appears in casual conversations, social media messages, gaming chats, and group texts. However, MB can have other meanings depending on the conversation, so looking at the surrounding messages can help determine what the sender intended.