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fifth wheel

noun

Simple Definition of fifth wheel

  • : an extra person who is not needed in a group

Full Definition of fifth wheel

  1. 1 a :  a horizontal wheel or segment of a wheel that consists of two parts rotating on each other above the fore axle of a carriage and that forms support to prevent tipping b :  a similar coupling between tractor and trailer of a semitrailer

  2. 2 :  one that is superfluous, unnecessary, or burdensome


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