Definition of "formalwear"

With their hair half up, and dressed demurely in black formalwear, they seemed like lost girls and conveyed little beyond a vague sense of urgency and dread; sure technicians all, they are not yet artists able to make their lashing limbs and inscrutable gestures mean something.

2007 April 10, Claudia La Rocco, “Austerity Meets Agitation While the Night City Glitters”, in New York Times‎