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. <mathematics> A problem of more than usual difficulty added to another on an examination paper.

6. [D. Rijder] 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. <chemical>

Rock material in a vein of ore, dividing it.

8. An interior rib occasionally fixed in a ship's hold, reaching from the keelson to the beame of the lower deck, to strengthen her frame.

9. 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.

<medicine> Rider's bone, 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.

(01 Mar 1998)