How is “a needle in a haystack” used?

In Room (2015), one line is: “Yeah, it's a needle in a haystack.”

Which movie is “a needle in a haystack” from?

The clip at the top of this page is from Room (2015).

Yeah, it's a needle in a haystack.

5 作品で登場 · 1 本目

a thing that is almost impossible to find

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a thing that is almost impossible to find
Like a needle in a haystack.

定義：Oxford Advanced Learner's Dictionary 第 9 版