IPA: /ˈheɪˌstæk/
KK: /ˈheɪˌstæk/
A large pile of dried grass that is stacked together, often found in fields.
The farmer stored the hay in a big haystack for the winter.
Haystack → The word is formed from "hay" (from Old English *heg*, meaning dried grass) and "stack" (from Old Norse *stakkr*, meaning a pile or heap). A haystack refers to a pile or heap of dried grass.
Think of a 'pile' ('stack') of 'dried grass' ('hay') — that's what a haystack is.