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1.
A science discovery which explains the phenomenon of what happens when 2 molecules of Vitamine "A" meet eachother once a week.

Due to the complexity of this phenomenon, there hasn't been much observation during "Ourdays" period.
Vitamine A1 : Hey you wanna do something every thursday?
Vitamine A2 : Yeah I'd love to! It'll be Ourdays!

*Vitamine A1 Never shows up*
by Aone November 28, 2009
 
2.
when everything seems to go your way, but not just for you, but for you and your friends (normally associated with smoking weed, but can happen anytime).
This one time, two guys blazed up and had to travel a long distance, then they found a tandem bicycle, "happy ourday" they said to one another.
by MrLaughter June 13, 2011
 
3.
When everything seems to go your way, but not just for you, but for you and your friends.
Friend: I got some dank weed

Then we smoked it all and walked to the store and got munchies.

Happy ourday amigo!
by mil1ion June 13, 2011