fifth wheel
The term 'fifth wheel' can refer to both a specific type of trailer hitch and an idiomatic expression for something unnecessary.
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Definition
B2Transport
(technical)A hitch mechanism on a truck or tractor used to connect and tow a trailer.
Example
- The truck was equipped with a fifth wheel to haul the large trailer.
- They used a fifth wheel hitch to connect the RV to their pickup truck.
B2Social Situations
(idiomatic, informal)A person who feels unnecessary or out of place in a group.
Example
- I felt like a fifth wheel at the party since I didn't know anyone there.
- Whenever they go out as a couple, she feels like a fifth wheel.
Similar
Terms that have similar or relatively close meanings to "fifth wheel":
third wheelbig wheelfifth columnspare tirefifth wallwagon wheeltraining wheel