expression, godan verb (-su)
outwit; get the better of; leave dumbfounded
Idiomatic expression meaning to outsmart someone, often by doing something unexpected that leaves them speechless or embarrassed. The literal image is 'exposing someone's nose', but it is used figuratively.
彼はライバルを鼻を明かすような作戦を考えた。
He came up with a strategy to outwit his rival.
新人の活躍でベテランは鼻を明かされた。
The veteran was left dumbfounded by the newcomer's performance.