庸俗
yōng sú · HSK 7
vulgar
🚽 庸俗 = 庸 (common/mediocre) + 俗 (custom/vulgar) — ordinary tastes sunk to crude, low ones
俗 (sú) by itself means custom or popular, and pairs with 庸 (yōng, mediocre/commonplace) to push the sense down to tacky, vulgar, debased taste. End sound sú rhymes with the oo in crude.
俗 — person radical 亻 + valley 谷
A semantic-phonetic compound: 亻 (person) gives the meaning and 谷 (gǔ/valley) suggests the sound. Originally referred to the customs and habits of common people living in the valleys, later extending to mean 'common,' 'vulgar,' or 'secular' as opposed to refined or religious.