# fifth wheel

> English word · Noun · IPA /ˌfɪfθ ˈʍiːl/

## Definitions
1. A type of trailer hitch, which consists of a horseshoe-shaped plate on a multidirectional pivot, with a locking pin to couple with the kingpin of a truck trailer.
2. A type of trailer hitch, which consists of a horseshoe-shaped plate on a multidirectional pivot, with a locking pin to couple with the kingpin of a truck trailer.
3. A horizontal wheel or segment of a wheel above the front axle and beneath the body of a carriage, forming an extended support to prevent it from overturning.
4. Anything superfluous or unnecessary.
5. Anything superfluous or unnecessary.

## Etymology
From the fact that since many vehicles such as carriages, coaches, wagons, prime movers, and trucks generally have four wheels on which they move, this component which resembles a wheel is the fifth.
* (anything superfluous or unnecessary): Sense 3 refers to the fact that a fifth wheel is not needed for a four-wheeled vehicle to operate.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/fifth-wheel