Other forms: haystacks
A haystack is a large pile of dried grass built to keep the rain out. Build a haystack, behind the haystack, a needle in a haystack.
Building one was a real skill: the shape sheds water and the hay must be dry enough not to heat, since a damp stack ferments and can catch fire on its own. Bales replaced them. A needle in a haystack means something impossible to find.
1nounhaystackA large pile of dried grass built to shed rain.
“The children climbed on top of the haystack and slid down.”
haystack is a pile.
Hay plus stack, recorded in Middle English. Stack comes from Old Norse stakkr, a haystack.
Middle English
haystak
English, today
haystack
From Middle English haystak, haystake, hey stak, equivalent to hay + stack.
Etymology from Wiktionary, CC BY-SA