woman-chaser; fool (for women)
Idiomatic use; often in the phrase 鼻毛を抜く or 鼻毛を読む, implying a man easily swayed by women. Sense 3 (fool) is a rare extension of this idea.
He's head over heels for her, like a fool who's had his nose hair plucked.
Standard kanji spelling.
Compound of 鼻 (nose) and 毛 (hair). The idiomatic sense likely derives from the image of a man so infatuated that he lets a woman pluck his nose hair without resistance.