The skirt has a side opening.

这裙子是侧面开口的。

《牛津词典》

Knitted jersey skirt with zipper for side opening.

弹力针织短裙，侧开拉链。

youdao

Some boxes used for ostomy products will now feature a perforated side opening. These boxes can still be opened from the top.

一些用于造口产品的盒子现在可以侧面开口了，同时也可以在上方打开。

youdao

She thought of her lover opening the door on the other side of which waited the sharp teeth of the tiger!

VOA: special.2009.04.18

The opening is big enough for perhaps six people to walk through, side-by-side.

VOA: special.2011.07.04

Managing our expectations is a double-edged sword: we need one side for opening ourselves to expansion, and the other, for warding off the expectations of others.

FORBES: Why Your Unhappy Personal Life Is Good For Your Career

Paul Jewell's Wigan did not look like a struggling side in the opening exchanges.

BBC: SPORT | Football | Premiership | Wigan 1-3 Bolton

England were the better side in the opening half in Newcastle with Rob Burrow scoring two of their four tries.

BBC: England 24-36 New Zealand