A "fifth wheel" refers to a type of trailer hitch that is mounted in the bed of a pickup truck. This design allows for better weight distribution and stability when towing larger trailers, such as RVs or horse trailers. The fifth wheel hitch connects to a special coupling on the trailer, providing a secure attachment point. In a broader context, the term "fifth wheel" can also describe someone who feels out of place in a social situation, similar to how a fifth wheel on a vehicle is unnecessary. This usage highlights feelings of exclusion or being an extra in a group, often in social gatherings or relationships.