Birth″day′ (bẽrth″dā′), n. 1. The day in which any person is born; day of origin or commencement.
Those barbarous ages past, succeeded next
The birthday of invention.
Cowper.
2. The day of the month in which a person was born, in whatever succeeding year it may recur; the anniversary of one's birth.
This is my birthday; as this very day
Was Cassius born.
Shak.