n. 1. The day in which any person is born; day of origin or commencement. [ 1913 Webster ]
Those barbarous ages past, succeeded next The birthday of invention. Cowper. [ 1913 Webster ]
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. [ 1913 Webster ]
This is my birthday; as this very day Was Cassius born. Shak. [ 1913 Webster ]
a. Of or pertaining to the day of birth, or its anniversary; as, birthday gifts or festivities. [ 1913 Webster ]