The Collaborative International Dictionary of English v.0.48:

Rumor \Ru"mor\, n. [F. rumeur, L. rumor; cf. rumificare,
   rumitare to rumor, Skr. ru to cry.] [Written also rumour.]
   1. A flying or popular report; the common talk; hence, public
      fame; notoriety.
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            This rumor of him went forth throughout all Judea,
            and throughout all the region round about. --Luke
                                                  vii. 17.
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            Great is the rumor of this dreadful knight. --Shak.
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   2. A current story passing from one person to another,
      without any known authority for its truth; -- in this
      sense often personified.
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            Rumor next, and Chance,
            And Tumult, and Confusion, all embroiled. --Milton.
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   3. A prolonged, indistinct noise. [Obs.] --Shak.
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WordNet (r) 3.0 (2006):

rumour
    n 1: gossip (usually a mixture of truth and untruth) passed
         around by word of mouth [syn: rumor, rumour, hearsay]
    v 1: tell or spread rumors; "It was rumored that the next
         president would be a woman" [syn: rumor, rumour,
         bruit]