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

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

This is because finding a world with the right atmosphere, chemistry, and geological activity is like hunting for a cosmic needle in a haystack, and this is why the search for extraterrestrial intelligence (SETI) has been such a struggle. —Rupendra Brahambhatt, Interesting Engineering, 13 Sep. 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

Multiple needles, multiple haystacks Technology plays a key role in helping CBP to stay one step ahead. —Adam Stone, USA Today, 15 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