From Longman Dictionary of Contemporary Englishnational costumeˌnational ˈcostume noun [countable, uncountable] SANDCCspecial clothing traditionally worn by the people of a particular country folk dancers in national costume
Examples from the Corpus
national costume• Stout Mrs Muller, in her national costume, sang.• Waiters in the silver national costume of Luctia bowed stiffly as they placed dish after lavish dish in front of the delegates. 