high-waist sideboob
An outfit with a high-waist style or bonded by something(like underbust, obi...) around below the bust, and baring the side skin above the waistline.(Also the area around Serratus anterior muscle )
It also can be a backless outfit, and often expose the sideboob or armpits.
Basically, the exposed side should go at least as low as the underbust line but not all the way down to the waist (hence "high-waist").
Examples
- Danbooru post #3289646: high-waist
- Danbooru post #3454337: underbust
Non-examples
- Danbooru post #7766803: exposed sideboob area does not reach underbust line