noun
vents at the hips of hakama
Refers to the side openings or slits at the hips of traditional hakama trousers, allowing freedom of movement.
この袴は股立が深くて動きやすい。
These hakama have deep side vents and are easy to move in.
Hakama are the traditional divided or undivided trousers; 股立 refers specifically to the hip vents on them.
Compound of 股 (momo, 'thigh') and 立 (tachi, 'standing'), referring to the standing or opening at the thigh area of hakama.