Definition of "riderless" [rid•er•less]

• Without or deprived of a rider. (adjective)

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• "Gwena was arrayed in the "riderless" version of Companion full dress; no saddle, but with a blue and silver blanket cut like her barding& decorated at all the points with silver bells, a blue-dyed leather hackamore with silver tassels at the cheekpieces, and reins bedecked with more silver bells."
• "On Thursday, six riderless horses led the 86th annual Rodeo Parade in Tucson."
• "The massive factory floor, which churns out heavy trucks and excavators, is patrolled by riderless robots."