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word of mouth
comments written online (about a product, service, etc.); online reviews
口コミで広まった店だ。
It is a shop that spread by word of mouth.
口コミサイトのレビューを参考にした。
I referred to reviews on a word-of-mouth site.
口コミが良い店ほどリピーターが増えて長く続く傾向がある。
Shops with better word-of-mouth tend to gain more repeat customers and last longer.