Define Half-birthday Meaning

a day approximately six months before or after the real anniversary of a person's birth. Typically celebrated by people who feel they are twice as important as everyone else or people who want to get more presents by coming up with a lame excuse.

I know you all are hot n popular and you have so many full birthdays to celebrate, so why should you bother with a half-assed attempt at your half birthday? Because it's the Best. Day. Of. The. Year. Nobody cares about your half birthday (please make no exception for mine), so do you and do it up, but don't do too much because it's your half birthday. I'm eagerly awaiting an invite to your halfway decent celebration.

You're birthday but half the way inbetween your birthday from the previous and next year (:

Two guy friends who have their birthdays exactly six months apart.