When a top, dress, leotard or bodysuit has an opening which exposes a lot of skin in the center of the body, including most or all cleavage, without fully exposing the breasts. This can be because it is the garment's intended appearance, or because the garment is intended to be opened & closed.
Note that both the top and bottom of the opening need to be visible from the front. If the gap in the garment continues up past the neck & shoulders, it is not an example unless the garment then closes the gap with a noticeable collar or a second garment is worn such that the gap is closed.
