Noun: fifth wheel
- Someone or something that is unwanted and unneeded
"He felt like a fifth wheel at the couples-only party";
- deadwood
- An extra car wheel and tire for a four-wheel vehicle
"He always kept a fifth wheel in his trunk in case of a flat tire";
- spare
- A steering bearing that enables the front axle of a horse-drawn wagon to rotate
"The fifth wheel allowed the wagon to make tighter turns"
Derived forms: fifth wheels
Type of: bearing, car wheel, redundance, redundancy, superfluousness
Encyclopedia: Fifth wheel