When a guy wears the waistband of his boxers above the waistline of his trousers. Then, whenever the guy’s shirt rides up/he stretches, the waistband of his boxers is visible.
This differs from normal sagging in that a guy does not wear his trousers lower than usual, rather he wears his boxers slightly higher, covering some of his stomach.
“Oh, did you see Connor semi-sagging earlier? He’s wearing his Calvin Klein’s today”