fifth wheel, n.
a steering bearing that enables the front axle of a horse-drawn wagon to rotate
<noun.artifact>
fifth wheel
semantic pointers
hypernym
an extra car wheel and tire for a four-wheel vehicle
<noun.artifact>
fifth wheel spare
semantic pointers
hypernym
someone or something that is unwanted and unneeded
<noun.attribute>
deadwood fifth wheel
semantic pointers
hypernym