slit pocket

基本解释

A slit in a garment, as in the back seam of a pocket.
开衩，衩：衣服上的狭长口子，如在口袋的后部缝口内。
odict.net
Flap pockets are additional fabric on covering the outside of the pocket opening. A high quality pocket allows both a slit pocket and flap pocket.
通常，滚边开叉口袋是一种理石装饰品，帽边口袋是附在口袋外延的附加材料。
blog.sina.com.cn
It is required to be double-besomed so that it becomes a slit pocket when the flap is inserted into the pocket. It gives alternate looks on a single suit.
优质口袋既可以当细缝口袋，又可以当帽边口袋，所以在一套衣服上有多种选择的外观。
blog.sina.com.cn