Waist cincher
From wipipedia.org

A waist cincher (waist cinch or waist nipper) is a short corset that only covers the waist and midriff, so it reduces the waist without covering the chest.
They typically have the same construction as a full size corset, as opposed to a corset belt that is constructed as a wide belt.
See also
- Bondage corset or discipline corset
- Hourglass corset
- Training corset
- Tightlacing