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

The best place to hide needles is in a haystack.

From MarketWatch • Jun. 10, 2026

Maven was built to find the needle in the haystack.

From Barron's • Apr. 5, 2026

This eliminates the costs and risks associated with pinpointing naturally occurring pockets of hot water, which are like needles in a haystack.

From The Wall Street Journal • Jan. 21, 2026

"It's like looking for a needle in a haystack," Pavia said.

From Science Daily • Nov. 13, 2025

Her sister peeked out from behind the haystack.

From "Finding Junie Kim" by Ellen Oh