Rider (noun)

1. A person who rides on horseback, a bicycle, etc.
2. A clause or provision added to a legislative bill, contract, etc.
3. A passenger on a public conveyance, especially a bus or train.
4. A person who participates in a sporting event on horseback.

Origin:

Middle english, from old english rīdan, from old norse rīða.

Examples:

1. She was an expert rider, trained in all the classical riding styles.
2. The bill was passed with riders attached to it.
3. He was a frequent rider of the city buses.
4. The horse show attracted many riders from around the country.
5. The young girl wanted to be a horse rider when she grew up.