fifth wheel

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fifth wheel

[¦fifth ¦wēl]
(mechanical engineering)
A coupling device in the form of two horizontal disks that rotate on each other positioned between a tractor and a semitrailer so that they can change direction independently.
References in periodicals archive ?
Commercial vehicles, trailers and fifth-wheel trailers are included in the definition.
Respondents predicted that consumers will continue to favor travel trailers (50 percent), followed by motorhomes (31 percent) and fifth-wheel trailers (17 percent).