Hay is grass which has been cut and dried so that it can be used to feed animals.
bales of hay.
一捆捆的干草。
make hay , make hay while the sun shines
If you say that someone is making hay or is making hay while the sun shines, you mean that they are taking advantage of a situation that is favourable to them while they have the chance to.
We knew war was coming, and were determined to make hay while we could.
我们知道战争即将来临,所以决定尽可能抓紧时机。