Meaning of 八つ口 in Japanese

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Definition of 八つ口

やつくち(yatsukuchi) 【八つ口 ·八口】

(n) small opening in the side of some traditional Japanese clothing (located where the sleeve meets the bodice, below the armpit)

みやつぐち(miyatsuguchi) 【身八つ口 ·身八口】

(n) small opening in the side of some traditional Japanese clothing for women and children (e.g. kimono, yukata) (located where the sleeve meets the bodice, below the armpit)