One's 21st birthday when they get completely piss drunk and throw up everything that is in their digestive tract including some internal organs. There is the possibility of throwing up to the extent that you end up swimming in your puke. If you don't know how to swim, you will die on your barfday because you will drown in your own stomach acid and partially digested food.
"I just woke up in the hospital after my epic barfday."
by brizzledho May 20, 2009
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One's 21st Birthday, when it's customary to drink 21-shots plus one for "good luck"
Jim: Hey, how was your birthday?

Kyle: I had 6 shots of JB, 3 of Jager, 5 of vodka, and chased the 8 shots of tequilla and I didn't boot.

Jim: Dude, you've got crazy tolerance, I'm glad you had a happy Barfday.

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Adam: Hey how was your 21st barfday?

John: I puked twice at the bar and woke-up face-down in the toilet. I don't remember anything else. It rocked!
by xchikax March 24, 2006
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What you say to someone when it's their birthday and they are drunk af and vomitting everywhere
John: this is the best birthday party ever! Oh no... (vomits)
Joe: Happy Barfday John!!!
by memes are dead October 3, 2016
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