noun
upper lip; philtrum; under the nose
Refers to the area between the nose and the upper lip, including the philtrum. Often used in expressions like 鼻の下が長い (to be soft on women).
彼は鼻の下に汗をかいていた。
He was sweating on his upper lip.
鼻の下を指でなぞった。
I traced my philtrum with my finger.
noun
Rarely used alone to mean 'mouth'; more common in set phrases like 鼻の下を伸ばす (to grin foolishly, especially at a woman).
彼は美人を見て鼻の下を伸ばした。
He grinned foolishly when he saw the beautiful woman.