bustier means: It is a garment that looks like a corset, but it’s more of a waist cinch than a brassiere. The garment can be worn at the waist, or it may extend to the hips. It was once an undergarment, sometimes called a “merry widow”. Now it’s worn as a top for women. The straps are usually removed and the fabric may include ornamental fabrics. (in Fashion Dictionary)

What else does bustier mean?

Form fitting, sleeveless, and often strapless top for women. Often worn as lingerie. (in Merlin Dictionary)