A clothes-swap party. People bring clothes, bags, or shoes they no longer wear, put them all together, and take home things other people brought. Nobody pays; you just swap. It is done partly to get "new" clothes for free and partly for the planet — the fewer clothes we buy, the less waste. The word came out of Britain in the 2000s and is used most in fashion writing, charity events, and green living. It is a friendly, light word — it sounds like the noise silk makes when it moves, which is exactly the feeling the people who made it up wanted. You will see "a swishing party", "a swishing event", or the verb: "we swished last weekend". Be aware that "swishing" much more often just means the -ing form of the ordinary verb "swish": moving with a soft brushing sound. A cow's tail swishing, a long skirt swishing on the floor, a basketball swishing through the net. The clothes-swap meaning is a small, newer, specialist use sitting on top of that ordinary one, and you can nearly always tell which is meant from what else is in the sentence.

（以物易物的）二手衣交換活動、換衣派對。大家把不穿的衣服帶來互換，不用錢。台灣近年也有這種活動，多半直接叫「舊衣交換」「衣物交換派對」。