hay /heɪ/ BrE AmE noun [uncountable]
[ Language: Old English ; Origin: hieg ]
1 . long grass that has been cut and dried, used as food for cattle
2 . make hay (while the sun shines) to take the opportunity to do something now, because you may not be able to do it later
3 . hit the hay informal to go to bed
⇨ a roll in the hay at ↑ roll 2 (10)