fifth wheel

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 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 trailer) that extends over the bed of the truck.
4.
an extra wheel for a four-wheeled vehicle.
5.
a superfluous, unneeded, or unwanted person or thing:
They enjoy making any outsider feel like a fifth wheel.
Origin
1870-75
Examples from the web for fifth wheel
  • Towing a fifth wheel trailer with a long bed truck increases the turning radius, but you might.
  • fifth wheel halves, not securely attached to vehicle.
  • The end of the kingpin is even with the top of the fifth wheel.
  • The slope angle of the road was measured by a sensitive electronic pendulum, and the distance was measured by the fifth wheel.
  • If you drop a trailer, use a fifth wheel lock whenever possible.
  • The kingpin, a part of the fifth wheel connection, is the pivot point between the tractor and semitrailer.
  • Truck designed primarily to pull a semitrailer by means of a fifth wheel mounted over the rear axle.
  • Large motor homes and fifth wheel units will not fit in the group camp area and should use the family campground.
British Dictionary definitions for 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 in Culture

fifth wheel definition


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

Slang definitions & phrases for fifth wheel

fifth wheel

noun phrase

A superfluous person or thing: I feel as though I'm a fifth wheel

[1902+; the date reflects the full form fifth wheel of the coach]


Idioms and Phrases with fifth wheel

fifth wheel

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.”