鼻の下を伸ばす

鼻の下を伸ばす (はなのしたをのばす) means to be infatuated with someone attractive.

Kana
はなのしたをのばす
Meaning
to be infatuated with someone attractive
Japanese Example
彼は美人を見るとすぐ鼻の下を伸ばす。
Translation
He immediately becomes infatuated when he sees a beautiful woman.