fifth wheel

[ fifth weel, hweel; often, fith ]

noun

1. a horizontal ring or segment of a ring, consisting of two bands that slide on each other, placed above the front axle of a carriage and designed to support the forepart of the carriage body while allowing it to turn freely in a horizontal plane.
2. a similar device used as a coupling to connect a semitrailer to a tractor.
3. a similar coupling between a heavy-duty pickup truck and a camping trailer fifth-wheel trail·er that extends over the bed of the truck.
4. an extra wheel for a four-wheeled vehicle.
5. third wheel ( def ):

   I decided not to go along on the canoe trip with him and his friends—I’d just be a fifth wheel.

fifth wheel

noun

1. a spare wheel for a four-wheeled vehicle
2. 1. the coupling table of an articulated vehicle
   2. a steering bearing that enables the front axle of a horse-drawn vehicle to rotate relative to the body
3. a superfluous or unnecessary person or thing

fifth wheel

1. A hanger-on; a person who serves no function: “The vice president felt like a fifth wheel after his exclusion from the committee.”

Word History and Origins

Origin of fifth wheel¹

First recorded in 1870–75

Idioms and Phrases

An extra and unnecessary person or thing, as in He was the only one without a date, so he felt like a fifth wheel . This expression, which alludes to an unneeded wheel on a four-wheel vehicle, may have originated as long ago as 1631, when Thomas Dekker wrote Match Me in London : “Thou tiest but wings to a swift gray Hounds heel, And addest to a running Chariot a fifth wheel.”

Example Sentences

When France discovered that the United States, Australia and Britain had secretly negotiated a submarine technology deal, effectively scuttling a separate Franco-Australian agreement, French officials mocked Britain as a “fifth wheel on the carriage.”

From Washington Post

The son attempted to back his truck and fifth wheel trailer from the street up the incline of the driveway, Huserik said.

From Seattle Times

“Great Britain in this matter is a bit of a fifth wheel on the carriage,” Le Drian said in the France 2 interview.

From Washington Post

“Gene therapy is taking a fifth wheel and putting it somewhere on the car and hoping it runs. Gene editing is repairing the flat.”

From Scientific American

Tiny houses are generally inexpensive, have more amenities than a travel trailer or fifth wheel, and are easily transportable from place to place.

From Washington Times