- See under fifth wheel(def 3).
- 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 body while allowing it to turn freely in a horizontal plane.
- a similar device used as a coupling to connect a semitrailer to a tractor.
- a similar coupling between a heavy-duty pickup truck and a camping trailer (fifth-wheel trailer) that extends over the bed of the truck.
- an extra wheel for a four-wheeled vehicle.
- a superfluous, unneeded, or unwanted person or thing: They enjoy making any outsider feel like a fifth wheel.
- a spare wheel for a four-wheeled vehicle
- the coupling table of an articulated vehicle
- a steering bearing that enables the front axle of a horse-drawn vehicle to rotate relative to the body
- a superfluous or unnecessary person or thing
A hanger-on; a person who serves no function: “The vice president felt like a fifth wheel after his exclusion from the committee.”
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.”