1.
word of mouth, online review
Information or opinions about products, services, or businesses spread informally between people, either in person or through online review platforms.
Writing
Written as 口コミ (mixed kanji and katakana). The コミ part is short for コミュニケーション (communication). Sometimes written entirely in katakana as クチコミ.
Usage
Originally referred to in-person word of mouth, but now overwhelmingly used to mean online reviews on platforms like Google Maps, 食べログ (Tabelog), and Amazon. The word carries a sense of peer-generated information as opposed to official advertising.