A moderately-sized rectangular gap between clothing that exposes the character's stomach. The total amount of exposed skin should equal no more than half the stomach’s surface; with waistline bottomwear the gap ends slightly above the navel, though it can shift to accommodate high-waist clothing.
Use midriff when there are regular clothes above (e.g. a crop top) and below (e.g. pants) the stomach, but the stomach is bare or visible beneath see-through clothing. "Regular" is not limited to real apparel.
