1a person who is riding or who can ride something, especially a horse, bicycle, motorcycle, or snowboard.
2a condition or proviso added to something already said or decreed:one rider to the deal—if the hurricane heads north, we run for shelter
an addition or amendment to a document, especially a piece of legislation:the rules of Congress make it difficult to attach a rider to an appropriations billa rider to an eligible life insurance policy
3a small weight positioned on the beam of a balance for fine adjustment.
late Old Englishrīdere 'mounted warrior, knight' (see ride, -er1)