Definition of: rider

(rī′dər) noun
1. One who or that which rides; a horseman; a bicyclist; specifically, one who breaks in horses.
2. Any device that rides upon or weighs down something else, actually or figuratively.
3. A separate piece of writing or print added to a document, record, or the like.
4. An addition or proposed addition to a legislative bill, adding to or modifying its original purport.
5. A metallic weight for use astride the graduated beam of a delicate balance.
6. The top rail of a rail fence.