- Your birthday is defined as the day on which you are born, or the annual anniversary of that day.
If you were born on July 1, then July 1 is an example of your birthday.
A little girl celebrating her birthday.
- the day of a person's birth or a thing's beginning
- the anniversary of this day
in one's birthday suit
Informal naked; nude
- The day of one's birth.
- The anniversary of one's birth.