overdressed
 US /ˌoʊ.vɚˈdrest/
 UK /ˌoʊ.vɚˈdrest/

1. 
formal demais, vestido demais
dressed too formally or elaborately for a particular occasion
:
• 
I felt completely overdressed at the casual backyard barbecue.
Senti-me completamente formal demais no churrasco casual no quintal.
• 
It's better to be slightly underdressed than overdressed.
É melhor estar ligeiramente subvestido do que formal demais.