underdressed

US /ˌʌn.dɚˈdrest/
UK /ˌʌn.dɚˈdrest/
"underdressed" picture
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.