1. used when reporting something you have heard but do not know to be true
rumour has it that they broke up, but I don't know for sure
A 'rumour' is a spoken story or piece of information where the truth has not been verified for certain. If you say 'rumour has it...' you are saying you have heard something but are not fully sure if it is in fact true. This is an informal phrase which is useful in social and professional contexts.