A traditional waistcoat, to be worn with a two-piece suit or separate jacket and trousers.French waistcoat in silk, circa 1750, LACMA.
A waistcoat (known as a vest in the United States) is a sleeveless upper-body garment. It is worn over a dress shirt and necktie, and below a coat as a part of most men's formal wear. It is the third piece of the three-piece male suit.