noun
mouthpiece; cigarette holder; filter tip
Refers to the part you put in your mouth, especially for smoking devices like a pipe or a cigarette holder; also used for the filter tip of a cigarette.
パイプの吸い口が汚れてきた。
The mouthpiece of the pipe has gotten dirty.
彼は銀の吸い口のついた煙草ホルダーを使っている。
He uses a cigarette holder with a silver mouthpiece.
noun
fragrant soup garnish
A small piece of aromatic ingredient (like yuzu peel or mitsuba) floated on clear soup (吸い物) for fragrance and visual appeal.
See also: 吸い物
吸い物に柚子の吸い口を浮かべる。
Float a yuzu fragrant garnish in the clear soup.
吸い物 is the clear soup itself, while 吸い口 is the fragrant garnish added to it.
Compound of 吸い (sui, 'sucking, inhaling', from 吸う) + 口 (kuchi, 'mouth'). The culinary sense derives from the idea of a small, aromatic 'mouthful' that enhances the soup.