Be on about something Definition 1 of 3Pro Tip 1/3Persistent Topic When someone constantly talks about the same subject, they're 'on about' it. Are you still on about moving to Canada? Pro Tip 2/3Potential Annoyance This phrase can imply that the speaker finds the topic repetitive or irritating. You've been on about that band for hours! Pro Tip 3/3Strong Interest Indicates the person has a deep interest in the topic. He's always on about environmental issues.