one who, or that which, drives; the person or thing that urges or compels anything else to move onward.-the person who drives beasts or a carriage; a coachman; a charioteer, etc.; hence, also, one who controls the movements of a locomotive.-an overseer of a gang of slaves or gang of convicts at their work.-a part that transmits motion to another part by contact with it, or through an intermediate relatively movable part, as a gear which drives another, or a lever which moves another through a link, etc. specifically:-the driving wheel of a locomotive.-an attachment to a lathe, spindle, or face plate to turn a carrier.-a crossbar on a grinding mill spindle to drive the upper stone.-the after sail in a ship or bark, being a fore-and-aft sail attached to a gaff; a spanker.