smart casual
US /ˌsmɑːrt ˈkæʒ.u.əl/
UK /ˌsmɑːrt ˈkæʒ.u.əl/

1.
smart casual, casual elegante
a dress code that is neat, conventional, and relatively informal, typically for a workplace or social event
:
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The invitation specified smart casual attire.
L'invito specificava un abbigliamento smart casual.
•
For the office party, the dress code is smart casual.
Per la festa in ufficio, il codice di abbigliamento è smart casual.