fifth wheel
US /ˌfɪfθ ˈwiːl/
UK /ˌfɪfθ ˈwiːl/

1.
quinto incomodo, persona di troppo
a person who is in a situation where they are not needed or are superfluous
:
•
I felt like a fifth wheel on their romantic dinner.
Mi sentivo come un quinto incomodo alla loro cena romantica.
•
When they started talking about their inside jokes, I knew I was the fifth wheel.
Quando hanno iniziato a parlare delle loro battute interne, ho capito di essere il quinto incomodo.