Edit
When a dress or skirt has a cutout slit. Either single or double and in some cases, accidental through fighting.
Most China dresses come with a side slit.
If a dress or skirt has high slits on both sides, it may form a pelvic curtain.
If the slit starts at the top of the skirt and doesn't go all the way down to the bottom, use hip_vent instead.
See also
The following tags are aliased to this tag: leg_slit (learn more).
The following tags implicate this tag: side_slit_shorts (learn more).