The feeling a child (or immature adult) gets when it's somebody elses birthday and not their own.

(Personally, I'm good as long as I still get cake and ice cream.)
Girl 1: "I can't wait until Monica sees what I bought for her birthday...what did you get her?"

Girl 2: "I'm not goin' to that stupid party! I wish it was my birthday!" (stomps off)

Girl 1: "Wow...talk about birthday envy."
by B. Robinson May 10, 2007
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When someone is celebrating a birthday, there is always one person in the group who gets as drunk or drunker then the person celebrating the birthday. This is generally a result of hanging out with the birthday person the whole night and thus weaseling in on many free 'birthday drinks', while also buying their own drinks.
Bob: "Yo, did you see Steve last night .... guy was a mess"

Tom: "Yah man, he was drunker then me, and it was MY birthday"

Bob: "haha, yah man, definite case of birthday envy"

Tom: "definite!"
by Adam SSS March 23, 2007
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