haystack

noun

hay·​stack ˈhā-ˌstak 

1

: a stack of hay

2

: a vertical standing wave in turbulent river waters

Examples of haystack in a Sentence

Recent Examples on the Web

According to scientists, detecting such an event in the Large Hadron Collider data is extremely rare and as difficult as finding a single needle in a haystack the size of an Olympic stadium. —Georgina Jedikovska, Interesting Engineering, 4 Nov. 2025

Each oceanfront room features a balcony looking out toward a towering haystack rock in the sea, plus gas fireplaces, pillow-top mattresses, and cast-iron soaking tubs. —Molly Allen, Travel + Leisure, 28 Oct. 2025

Microsoft’s experiment started when the researchers wanted to demonstrate how AI could tackle the needle-in-a-haystack problem of finding useful new materials and chemicals. —Andrew Moseman, IEEE Spectrum, 1 Oct. 2025

There’s trying to find the needle in the haystack, and then there’s building a better magnet. —Expert Panel®, Forbes.com, 20 Aug. 2025

Word History

First Known Use

15th century, in the meaning defined at sense 1

Phrases Containing haystack

• a needle in a haystack

Rhymes for haystack

• aback
• anzac
• attack
• backpack
• backtrack
• bareback
• blackjack
• brownback
• buyback
• callback
• cognac
• comeback

Kids Definition

haystack

noun

hay·​stack -ˌstak 

: a stack of hay