expression, noun
pretending not to see; turning a blind eye; closing one's eyes to
Often used in the phrase 見て見ぬふりをする (to see and pretend not to see). Describes the act of deliberately ignoring something one has noticed.
See also: 見て見ぬふり
彼は私の失敗を見ぬふりをしてくれた。
He pretended not to see my mistake.
いじめを見ぬふりするのはよくない。
It's not good to turn a blind eye to bullying.
A longer, more explicit phrase meaning 'to see and pretend not to see'; 見ぬふり is often used as a shorter equivalent.
From 見ぬ (archaic negative of 見る, 'to see') + ふり ('pretending'). The phrase literally means 'pretending not to see'.