The phrase "high slit" refers to a cut or opening in a piece of clothing, such as a dress or skirt, that goes up higher on the leg than usual, revealing more skin. Full definition
I kept things light by adding a white bucket bag, my favorite pink pumps and a mint sweater with high slits on the side that happen to look great with high waisted skirts and jeans. (stylewich.com)
This jumpsuit has spaghetti straps, a v - neckline, and thigh high slits on both legs. (sophieandtrey.com)
We are loving the floral print and the thigh high slits in this piece! (showpo.com)