Rider

n.	1.	One who, or that which, rides.
	2.	Formerly, an agent who went out with samples of goods to obtain orders; a commercial traveler.
	3.	One who breaks or manages a horse.
	4.	An addition or amendment to a manuscript or other document, which is attached on a separate piece of paper; in legislative practice, an additional clause annexed to a bill while in course of passage; something extra or burdensome that is imposed. After the third reading, a foolish man stood up to propose a rider. - Macaulay. This [question] was a rider which Mab found difficult to answer. - A. S. Hardy.
	5.	(Math.) A problem of more than usual difficulty added to another on an examination paper.
	6.	A Dutch gold coin having the figure of a man on horseback stamped upon it. His moldy money ! half a dozen riders. - J. Fletcher.
	7.	(Mining) Rock material in a vein of ore, dividing it.
	8.	(Shipbuilding) An interior rib occasionally fixed in a ship's hold, reaching from the keelson to the beams of the lower deck, to strengthen her frame.
	9.	(Naut.) The second tier of casks in a vessel's hold.
	10.	A small forked weight which straddles the beam of a balance, along which it can be moved in the manner of the weight on a steelyard.
	11.	A robber. Rider's bone (Med.) a bony deposit in the muscles of the upper and inner part of the thigh, due to the pressure and irritation caused by the saddle in riding.

Noun	1.	rider - a traveler who actively rides an animal (as a horse or camel)
	2.	rider - a clause that is appended to a legislative bill
	3.	rider - a traveler who actively rides a vehicle (as a bicycle or motorcycle)
	4.	rider - a traveler riding in a vehicle (a boat or bus or car or plane or train etc) who is not operating it Synonyms: passenger

RIDER, practice, legislation. A schedule or small piece of paper or parchment added to some part of the record; as, when, on the reading of a bill in the legislature, a new clause is added, this is tacked to the bill on a separate piece of paper, and is called a rider.

addendum, affix, allonge, appendix, bidet, bill, broncobuster, buckaroo, caballero, calendar, carriage horse, cart horse, cavalier, cavalry horse, cavalryman, chevalier, circus rider, clause, coda, codicil, commentary, companion bills amendment, cowboy, cowgirl, cowpuncher, draft horse, dragnet clause, dray horse, driving horse, enacting clause, enclitic, envoi, epilogue, equestrian, equestrienne, escalator clause, fill horse, filler, gaucho, gigster, hack, hackney, hold-up bill, horse soldier, horseback rider, horsebacker, horseman, horsewoman, hunter, infix, interlineation, interpolation, jockey, joker, jument, knight, lead, leader, marginalia, motion, mount, mounted policeman, note, omnibus bill, pack horse, palfrey, plow horse, pole horse, polo pony, post-horse, postboy, postilion, postscript, prefix, privileged question, proclitic, proviso, puncher, question, remount, riding horse, road horse, roadster, roughrider, rouncy, saddle horse, saddler, saving clause, scholia, shaft horse, stalking-horse, steeplechaser, suffix, sumpter, sumpter horse, supplement, tail, thill horse, thiller, trick rider, vaquero, wheeler, wheelhorse, workhorse