haystack

American  

[hey-stak] / ˈheɪˌstæk /

noun

1. a stack of hay with a conical or ridged top, built up in the mowed field so as to prevent the accumulation of moisture and promote drying.

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haystack British  

/ ˈheɪˌrɪk, ˈheɪˌstæk /

noun

1. a large pile of hay, esp one built in the open air and covered with thatch

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haystack Idioms  

1. see needle in a haystack.

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Etymology

Origin of haystack

1425–75; late Middle English. See hay, stack

Explanation

A haystack is a pile or bundle of hay. On farms, after hay has been cut, it's formed into haystacks until being fed to farm animals. Haystacks come in different shapes and sizes, including piles of rectangular blocks of hay; rounded bales; and pointed piles of hay. These haystacks are all packed tightly, and they're often covered to protect them from the rain. You've probably heard the phrase "a needle in a haystack," an idiom that's used when a search is on for some impossibly tiny thing that's lost.

Example Sentences

Maven was built to find the needle in the haystack.

From Barron's • Apr. 5, 2026

Clough added, "As microplastic researchers looking for microplastics in the environment, we're searching for the needle in the haystack, but there really shouldn't be a needle to begin with."

From Science Daily • Mar. 29, 2026

While picking a big winner is like finding a proverbial needle in a haystack, it’s much easier than in 1926.

From The Wall Street Journal • Mar. 23, 2026

Another rescue volunteer, named Justin, compared the effort to "trying to find a single hay in a haystack".

From BBC • Jul. 8, 2025

Sergio takes us to a little area near the barn where my mom has to stand on a haystack to get reception.

From "Marcus Vega Doesn't Speak Spanish" by Pablo Cartaya