Sharara

Sharara or a Gharara, originated in the city of Lucknow during the era of the Nawabs. During the late 19th and early 20th centuries, it was considered everyday attire among women of the North Indian Muslim upper classes. A gharara is a traditional garment, worn primarily by women in the Indian Subcontinent. It consists of a kurti (a short, mid-thigh length tunic), a dupatta (veil), and most importantly, a pair of wide-legged pants, so they flare out dramatically. 

It resembles a gown so much. Hence, it befits ethnic as well as western wear. I highly recommend that you have one in your wardrobe for a formal wear.