underdressed
US /ˌʌn.dɚˈdrest/
UK /ˌʌn.dɚˈdrest/

1.
mal vestido, vestido de forma informal
wearing clothes that are too informal for a particular occasion
:
•
I felt completely underdressed at the fancy restaurant.
Me sentí completamente mal vestido en el restaurante elegante.
•
She was worried she would be underdressed for the gala.
Le preocupaba estar mal vestida para la gala.