hip vent
Gaps like those found at the sides of the waistband of a hakama. Present in highly exaggerated form in the costumes of Ibuki, Akashi, and Ooyodo.
If the gap goes all the way down to the hem, use side slit (and possibly also pelvic curtain) instead.
See also
The following tags are aliased to this tag: hip_cutout (learn more).