Fly off on a tangent is an idiomatic expression, which means to deviate from the main topic of discussion and start discussing something irrelevant. There are several synonyms for this phrase, including go off on a tangent, veer off on a tangent, stray off on a tangent, get sidetracked, drift off topic, go astray, digress, go off at a tangent and deviate from the point. It is important to stay on topic and refrain from straying, as doing so can cause confusion and disrupt effective communication. Using these synonyms can help you convey your message more effectively and stay focused on the main point of discussion.