If something is rumoured, people are passing a story around, but nobody is standing behind it as a hard fact. You hear it from a friend, from “they say”, or from a paper that is being careful: “It is rumoured that the shop will close.” The speaker is not promising it is true — they are only reporting the talk. Though actually, a rumour is not always a whisper in a corner. It can be on every phone in town by lunch and still be only a rumour until someone proves it. The shape you will meet most is it is rumoured that… or she is rumoured to be… — so the person is not doing the rumoured thing; the talk is happening around them. It feels a little cooler and more grown-up than gossip, but it is still unofficial. Teachers, newspapers, and office chat all use it when they want to share a story without putting their name on it. British spelling keeps the u (rumour, rumoured); American spelling drops it (rumor, rumored). Same word, same meaning.