look up any word, like half chub:
 
1.
When it Hays a lot during the night and then the next day there is so much hay you can not get out of your house. And as such you have a totally awesome time.
Dude1:Dude! We got a hayday today!
Dude2:Yea dude these come once in a blue moon!
by Drpepperx December 13, 2010
 
2.
when an upper classman or group of upperclassmen designate a day to go beat the living hell out of any underclassmen that gets in there way or just looks like they could use a good beating
next tuesday im having a fuckin hayday with all those annoying freshman!
by pure justice August 22, 2008
 
3.
What a retired hockey player refers to as their time when they were playing hockey.
"Back in my hay days I kicked some ass"-Ken Daneyko
by belcherrr February 21, 2008