Rider

noun

1. One who rides, often on a horse or a motorcycle.
2. A provision annexed to a bill under the consideration of a legislature, having little connection with the subject matter of the bill.
3. (by extension) Something extra or burdensome that is imposed.
4. An amendment or addition to an entertainer's performance contract, often covering a performer's equipment or food, drinks, and general comfort requirements.
5. An additional benefit attached to an insurance contract.