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

1.
vela, pessoa desnecessária
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.
Eu me senti como uma vela no jantar romântico deles.
•
When they started talking about their inside jokes, I knew I was the fifth wheel.
Quando eles começaram a falar sobre suas piadas internas, eu soube que era a vela.