deadhead

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A person who uses a free ticket for admittance, accommodation, or entertainment.
2. n. A vehicle, such as an aircraft, that transports no passengers or freight during a trip.
3. n. A person regarded as dull-witted or sluggish.
4. n. A partially submerged log or trunk.
5. v. To pilot or drive (a vehicle) carrying no passengers or freight.
6. v. To pull (dead or dying blossoms) off a flower.
7. v. To make a trip without passengers or freight: "The instruments were out, and it meant they had to deadhead back on another airplane” ( Walter J. Boyne).
8. v. To bypass a senior employee in order to promote a more junior employee.
9. adv. Without passengers or freight; empty.

Century Dictionary and Cyclopedia

1. n. In founding: The extra length of metal given to a cast gun. It serves to receive the dross, which rises to the surface of the liquid metal, and would he, were it not for the dead-head, at the muzzle of the gun. When cooled and solidified, the dead-head is cut off. Also called sinking-head or sprue.
2. n. The tailstock of a lathe. It contains the dead-spindle and back-center, while the live-head or headstock contains the live-spindle.
3. n. Nautical, a rough block of wood used as an anchor-buoy.
4. n. One who is allowed to ride in a public conveyance, to attend a theater or other place of entertainment, or to obtain any privilege having its public price, without payment.
5. To provide free passage, admission, etc., for; pass or admit without payment, as on a railroad or into a theater: as, to deadhead a passenger, or a guest at a hotel.
6. To travel on a train, steamboat, etc., or gain admission to a theater or similar place, without payment.
7. n. In lumbering, a sunken or partly sunken log.

Wiktionary

1. n. A person either admitted to a theatrical or musical performance without charge, or paid to attend
2. n. An employee of a transportation company, especially a pilot, traveling as a passenger for logistical reasons, for example to return home or travel to their next assignment.
3. n. Anyone traveling for free.
4. n. A train or truck moved between cities with no passengers or freight, in order to make it available for service
5. n. A person staying at a lodging, such as a hotel or boarding house, without paying rent; freeloader.
6. n. A stupid or boring person; dullard
7. n. slang Driftwood.
8. n. slang A fan of the rock band the Grateful Dead (usually Deadhead).
9. n. slang A zombie.
10. v. intransitive To travel as a deadhead, or non-paying passenger.
11. v. transitive, intransitive To drive an empty vehicle.
12. v. transitive To send (a person or message) for free.
13. v. transitive To remove spent or dead blossoms from a plant.

GNU Webster's 1913

1. adj. (Naut.) a rough block of wood used as an anchor buoy.
2. n. Colloq. U. S. One who receives free tickets for theaters, public conveyances, etc.
3. n. (Naut.) A buoy. See under Dead, a.

WordNet 3.0

1. n. a train or bus or taxi traveling empty
2. n. a nonenterprising person who is not paying his way